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By O. D. Maurice

Feldspar mining in Canada came to an end during 1972 after many years of continuous activity. The deposits are not exhausted and the domestic demand for this product is expected to continue at about the same level as in recent years. The size of the industry does not justify the installation of expensive equipment in the mills, but it is believed that a modest profit could be made by a small operation using rudimentary methods of separation. Largescale and accurate mapping of the pegmatite dykes could help in planning mining operations for a better recovery of a uniform product.

Jan 1, 1973

By S. Balideh

A good understanding of the behavior of rock helps us to make more informed decisions regarding geo-structures. Engineers need accurate equations to calculate the strength and deformation of rock before and after failure. Previous studies explain the failure of rock to ultimate strength, and laboratory tests adequately determine the ultimate strength and deformation modulus of rock. However, there are few comprehensive equations to determine the post-failure strength and deformation of rock. Previous work shows that the post-failure behavior of rock depends on the behavior of the broken rock particles after failure. The following question is then posed: How can the post-failure behavior of rock be determined by the behavior of broken rock particles? In order to answer the question, this study pursues three objectives: (i) to explain the behavior of broken rock at low confining pressure; (ii) to estimate the behavior of broken rock via the extrapolation of scaled laboratory testing; and to suggest a procedure (iii) to outline the post-failure behavior of a rock mass at low confining pressure commensurate with the behavior of broken rock in a rock mass.

Aug 1, 2013

By Yolaine le Beau

Plan de la présentation Le contexte mauritanien La situation de l?environnement en 1999 L?évolution de 1999 à 2010 Bilan La situation de l?environnement en 2011 Le contexte mauritanien Pays du Maghreb couvert à 75% par le désert du Sahara Un des plus pauvres au monde Index de développement humain : 136esur 169 pays en 2010 46,7% de la population ne peut subvenir à ses besoins quotidiens

May 1, 2011

By E. O. Lilge

THE USE of the Driessen cone as a heavy-media concentrator involves a mineral dressing process in which many variables inherent in the ore and in the process may have an effect on the efficiency of mineral separation and the operation of the cone. The magnitude of these effects and their possible interrelationships must be known before a full-scale plant can be designed and built. It appears that, among the most important variables, are the following: Ore Variables: The particle size of feed The difference in specific gravity between economic and non-economic minerals The intimacy of mineral association Cone Variables: Cone inlet area Ore to media ratio Cone ratio Size distribution in heavy media Specific gravity of media Viscosity of media Type of media

Jan 1, 1956

By M. R. Julien, A. Maqsoud, J. Martschuk, B. Bussière

Acid mine drainage (AMD) from mine wastes is one of the most challenging environmental problems currently facing the mining industry. When mining wastes have the potential to produce AMD, the effluents produced have to be managed to meet existing regulations on water quality. The LTA impoundment (property of Barrick Gold Corp.) located near Malartic, Quebec, contains sulphide tailings that have the potential to generate an acidic leachate. The closure option selected by Barrick was to construct a cover with capillary barrier effects (CCBE), in which the moisture- retaining layer is made of non-acid-generating tailings. Since its construction in 1996, the cover has been monitored to evaluate its performance. For that purpose, various parameters have been measured, including the volumetric water content and matric suction in the different layers of the cover. This paper presents some of the main results from the monitoring program that started eight years ago. The results show that the cover is able to maintain a high degree of saturation in its moisture- retaining layer, acting as an oxygen barrier. The actual performance of the CCBE on the flat surface of the 60 ha site is better than expected at the design stage. The only concern with the LTA cover is the effect of slopes that can reduce the performance of the CCBE during dry periods. However, these effects appear only for short periods of time, and are limited to very localized areas, so that they do not significantly affect the overall performance of the CCBE and its ability to limit the production of AMD.

Jan 1, 2006

By Guoxiang Chi

This paper consists of two parts: the first part describes the principles and functionality of the BsnMod program, and the second part presents preliminary application of this program to paleo-fluid flow modeling in the Anticosti Basin. The BsnMod program simulates fluid flow and heat transfer during the evolution of sedimentary basins through numerical solution (finite difference method) of three partial differential equations, which describe sediment compaction, fluid continuity, and heat conservation. It can be used to estimate the evolution of fluid overpressure, flow rate, and temperature during the basin history. The program was written in C++, works under Windows environments, and has a user interface allowing inputs in dialogues and outputs in both tabular and graphic forms. The program was applied to the Lower Paleozoic Anticosti Basin in eastern Canada. The basin history consists of a passive margin stage and a foreland basin stage. Preliminary simulation results indicate that no significant fluid overpressures were developed in the passive margin stage and during the early period of the foreland basin stage, but strong overpressures were developed within the foreland basin succession during the middle and late periods of the foreland basin stage. Fluid flow rates were generally slow, and thermal profiles were not significantly disturbed by fluid movement throughout the basin history. Potential source rocks of hydrocarbons were found in the foreland basin succession. The strong overpressures in the foreland basin succession could have been a major driving force for hydrocarbon migration from the source rocks to the underlying potential reservoir rocks.

May 1, 2001

By J. W. Choung, T. Fu, Z. A. Zhou

An on-line visualization technique and methodology was developed to investigate the role of fine sphalerite (< 10 um) aggregation in flotation. The images of particle aggregates under different operating conditions were recorded and analyzed. The effect of impeller design on particle aggregation was demonstrated. This difference was not mainly due to the energy input into the system, but due to the resultant hydrodynamic conditions created by the impeller and their effect on particle interactions. The recorded image showed that adding fine silica (- 5 um) did not interfere with fine sphalerite aggregation, thereby showing no effect on the sphalerite recovery. Effect of the enlarged aggregate size on increasing flotation recovery was confirmed. Although Malvern Mastersizer produced consistently lower estimates of aggregate size than those by the image analysis, both methods responded to the changes in operating conditions in the similar trend. It was shown from this study that on-line visualization technique is a powerful tool for studying fine particle aggregation and morphology in the context of diagnosis for the flotation separation.

Jan 1, 2004

By Robert B. Parsons

"In this period of improved metal prices and reported profits, valuable lessons should be recalled from the 1970s when a similar cycle lured the federal and provincial governments into thinking that they could grab bigger pieces of the pie without harming the minerals industry. It took years for the industry to recover from the damage inflicted by that unprecedented scramble for higher tax revenues. It is hoped that the current policy makers will have learned from the lessons of the seventies, and will realize that mining companies need to keep a reasonable share of profits realized during the good years in order to prepare for the inevitable downturn in the cycle.INTRODUCTION"", «. We have made clear to industry that super profits... will no longer be tolerated "".With that assertion, the Honourable David Barrett , Premier and Minister of Finance of the Province of British Columbia, announced the introduction of a new mining tax regime in his February 17, 1974 bud get papers . British Columbia producers would face a basic royalty and a royalty on so-called ""super profits"", resulting in some instances in tax rates exceeding 100070 of pre-tax profits.The ball started to roll. Mining tax changes knew no political or geo graphical boundary. On April 9, 1974, Ontario&apos;s Treasurer John White stated in his budget speech:""Increased demand by major industrialized countries has resulted in sharply higher metals prices and substantial wind fall gains for the mining industry in Ontario. With the prospective demand for minerals likely to sustain current price trends into the future, it is only fair that we secure for the people a higher return from our natural resources""."

Jan 1, 1989

By W. A. Bell

The Carboniferous system of rocks in the Maritime Provinces include as workable mineral and organic substances, gypsum, anhydrite, salt, coal, building stones, grindstones, limestones, brick-clay shales, fire-clay shales, oil shales, etc. The system is, therefore, pre-eminently of economic value to the provinces in which it occurs, and the more knowledge we may gain concerning it, the more we may be prepared to aid in the development of these useful substances. For this purpose it is not sufficient to state that the ground upon which we stand is underlain by Carboniferous rocks. In-discriminate digging or drilling will not open many new mines of wealth, however difficult it may be to dampen the optimism of gamblers. For mineral wealth has not been scattered in the rocks haphazard, now here, now there, but its distribution has been the result of natural earth forces acting at intervals throughout the countless millions of years that have elapsed since our planet was born. As regards the majority of metalliferous deposits, the earth forces involved have resulted in the penetration of surface or sub-surface rocks by molten rock-matter and associated mineral solutions from deep-seated sources. But the economic Carboniferous deposits that have been mentioned are themselves types of bedded surface rocks rather than immigrant deposits, and their formation and geological history is closely related to that of the rocks with which they are interbedded.

Jan 1, 1924

By Robert D. Brown

"All ten Canadian provinces have now tabled their 1981 /82 budgets . Only the provinces of Ontario, Quebec and British Columbia made more than minor modifications to their tax structures, with both Ontario and Quebec imposing major tax increases. In the past year, the federal budget was also released in the spring. Not so this year: we have that to look forward to in the fall!This month, Tax Notes presents a brief summary of the more significant tax changes introduced at the provinciallevels in the last months.Summary of provincial tax rate changesThe tax changes in this year&apos;s provincial budgets were both up and down- but there were far more tax increases than tax cuts.At the corporate tax level, two provinces, New Brunswick and British Columbia, increased their general corporate income tax rate; the former by two percentage points and the latter by one percentage point. Quebec, rather unexpectedly, sharply cut its corporate tax rate on business income, but increased some of its other business taxes at the same time. British Columbia reduced its corporate tax rate on small business income by two percentage points and Saskatchewan by one percentage point."

Jan 1, 1981

By T. R. Skerry, H. P. Hudson, T. E. Warren

"ALTHOUGH coal is generally the cheapest fuel on the basis of heating value it has been at a disadvantage in competition with other fuels because means have not been available for efficient •Conversion of its thermal energy to mechanical work. Taking the •railway application •as an example, the cost of Diesel oil is about three times that of its thermal equivalent in coal, but the overall efficiency of a Diesel locomotive is about five times that of a coal-fired steam locomotive. Accordingly, the Canadian railways are replacing all coal-fired steam Locomotives, as they are retired from service, with Diesel units. This conversion in itself represents a major loss to the coal industry because the value of railway fuel is approximately 130 million dollars per year, and there are other applications in the medium power range where oil is displacing coal. There is, therefore, a strong incentive to attempt development of an efficient coal-burning engine.Coal has never been a promising fuel for reciprocating internal combustion engines because of the time required for its combustion in pulverized form . This is not less than one-tenth of a second so that the speed of such an engine would have to be very slow. There are also serious difficulties of a mechanical nature arising from the necessity for intermittent combustion and the use of close-fitting pistons."

Jan 1, 1952

By John H. Morris, R. Gwilym Roberts

"The Upper Beaver Mine, Kirkland Lake, Ontario, is a copper-gold deposit in mafic flows and sedimentary rocks. The deposit consists of a number of orebodies of two types: copper- and gold-bearing chalcopyrite-pyrite-magnetite ore; and gold-bearing quartz veins. Chalcopyrite-pyrite-magnetite ore occurs in two structural forms: as cherty interflow material in coarse clastic roks underlying flows; and as veins. Both sedimentary and vein ore occur in each orebody. The goldbearing quartz veins occur in interflow sedimentary units and at the contacts of oligoclase porphyry dykes.The deposit is in a localized, volcanic-sedimentary basin which began to develop during the emplacement of the upper units of the pyroclastic and sedimentary Gauthier Group, and continued to the early mafic flow activity of the overlying Kinojevis Group. The formation of the volcanic-sedimentary basin is ascribed to the D0 deformation. The deformation is significant in terms of the structural configuration in the mine area, and may be significant regionally, but this has not been demonstrated. The early deformation was followed by two tectonic deformations. D 1 is associated with a penetrative mineral foliation, axial planar to upright mesoscopic folds and striking parallel to the trend of regional fold structures. Mesoscopic flexural-slip folds, kink folds and fracture-crenulation cleavage are attributed to the D2 deformation. It is probable that no large-scale fold structures are associated with the D2 deformation. The gold-bearing quartz veins were folded during the D1 deformation.The close spatial relationship of copper-gold, chalcopyritepyrite- magnetite veins with chalcopyrite-pyrite-magnetite in cherty inter flow material is strong evidence for the derivation of the veins from the sedimentary ore by hydrothermal, metamorphogenic processes. By analogy, it is suggested that the gold-bearing quartz veins were formed by similar processes."

Jan 1, 1982

By A. R. Trusiak, C. Bazin, D. Hodouin

"The On-Stream Analyzer has proven, and is still proving to be, an extremely valuable tool for the control of flotation circuits. This paper examines the possibility of going further in the utilization of the analyzer results by using a real-time material balance program to calculate the mass flow rates within the streams of a circuit for process control, analysis and optimization as well as for the detection of sensor malfunction. The material balance algorithm improves measurements and give good estimates of unmeasured variables during normal operating conditions. The potential and limitations of the method are illustrated using results of an application to the Line 3 flotation circuit of Brunswick Mining and Smelting, New Brunswick.IntroductionThe On-Stream Analyzer (OSA) has gained, over the last two decades, the status of key instrument for the control of flotation plants. The OSA is currently used in almost every sulphide flotation plant and its application in oxide mineral flotation plants isincreasing. Commercial OSAs include a sampling system that collectssamples from various streams of a circuit and exposes thesamples to an X-ray beam. The sample then generates X-ray pulsesthat are converted into assays using multilinear regression programs(Leroux and Franklin, 1994). The estimated assays arepassed to the flotation operators via operator consoles, or to controlloops of various degrees of complexity (McKee, 1991), whichmanipulate reagent addition, aeration rate or froth thickness toensure an adequate operation of the plant. Although this applicationrapidly pays for the purchase of the OSA, one should ask:""Could we get more from the OSA?"""

Jan 1, 1995

By K. Aziz

The solutions to unsteady-state gas flow in a radial system have been reviewed in order to aid in the interpretation of drawdown data. It has been the practice to evaluate the time and rate conversion constants, directly or indirectly, by using reservoir data. This paper presents a method of determining these constants from drawdown data. A simplified approach to the de-termination for the various boundary conditions is presented. An example of a problem which illustrates the use of this theory appears in the appendix. UNSTEADY-STATE FLOW EQUATION The solution of any unsteady-state flow problem involves (1) the continuity equation, (2) the equation of state of the fluid, (3) the equation of fluid motion and (4) the boundary conditions. For the Darcy flow of a gas in the horizontal radial plane, the equation is when the viscosity, compressibility and permeability to gas flow may be assumed constant and the medium

Jan 1, 1963

By J. G. Whellock, J. W. Matousek

"In spite of their importance to the economics of many metallurgical projects, the values and technical aspects of precious metals losses in smelting operations are relatively undeveloped subjects. This paper attempts to provide a condensed overview of precious metals losses in pyrometallurgy, using some of the limited production and experimental data available. It is intended for three general groups of metallurgists - operators attempting to improve recoveries, cost-accounting engineers making estimates of metal losses in new or modified smelting plants, and research engineers and students.Distribution coefficients of precious metals, the ratios of metal or matte assays to slag assays, are convenient means of comparing smelting processes and the tendencies of the different metals to enter the slag. For silver in lead blast furnaces this ratio is approximately 250;for gold and the platinum group metals in submerged-arc, electric furnaces it is 900. The ratio for gold and PGMs in converters varies with the degree of oxidation of the charge. The over-all cycle-average for industrial installations is tentatively estimated to be 35.IntroductionThe magnitude of precious metal s losses in pyrometallurgical operation s is difficult to assess. The primary producers are generally reluctant to discuss the subject. The by-product producers (the large sulphide smelters o f copper , nickel, and lead) might be more willing to disclose information, but these have precious metals in their feeds in such dilute quantities that accurate accounting is extremely difficult. It is not until numerous processing steps have been taken t hat the precious metals become sufficiently concentrated to permit acceptably accurate sampling and analytical procedures to be followed. Thus, knowledge of the precious metals contents o f the intermediate mattes and slags may simply be unavailable."

Jan 1, 1990

By Lawrence Devon Smith

The Business Case for Sustainable Development ?What are SD & TBL? ?Investment Funds & Fund Managers ?Banks and Risk Aversion ?The Dilemma of Juniors ?Meet Your New Partners ?The Cost of Problems ?The Cost of Delays Sustainable Development ?Humanity has the ability to make development sustainable -to ensure that it meets the needs of the present without compromising the ability of future generations to meet their own needs.? Our Common Future BrundtlandCommission, 1987

May 1, 2003

By David Thomas, Charles Harper, Brian Watters

The Star-Waddy Lakes area lies withjn the northeasterly-trending early- to mjd-Proterozoic volcanoseilimentary-pl utoruc belt referred to as the La Range Domllin. In the area investigated the domajn is composed of the Central Metavolcaruc Belt which is bordered by metasedimentary belts of the Crew Lake and MacLean Lake Belts to the northwest and southeast respectively. The boundaries between the Central Metavolcanic Belt and the flanking belts are generally marked by prominent zones of shearing. The volcanosed imentary succession is intruded by a variety of ultramafic to felsic plutons which, on the basis of lithology, field relations and geochronology, can be broadly subdivided into three groups or episodes. These are: a) an 'early' (ea. 1866 Ma), possibly subvolcanic, episode marked by composite intrusions ranging from gabbro-diorite to granite, b) an 'intermediate' (ea. 1854 Ma) plutonic event distinguished by more homogeneous felsic intru ions ; and c) a 'later' (ea. 1835 Ma) event characterized by leucocratic quartz-rich grani te intrusions. The La Range Domain has undergone polyphase deformation with a strongly developed northeast-trending structural grain. Large scale folding is manjfested by large regional sy nforms, arcuate and triangular patterns associated with many of the plutons and by tight to isoclinal folds within the adjacent metasedimentary belts. Inhomogeneous strain characterizes much of the Star-Waddy Lakes area. With strain gradients being typically very steep, zones of high strain consisting of zones of extreme extensional fabrics, discrete shearing, as well as broader zones of cataclasis and structural slicing, are often juxtaposed with areas of relatively minimal deformation . Dilation structures tend to favour these zones of highly contrasting strain. Late, brittle fractures, faults and shear zones are widespread and appear to be particularly important as loci for gold mineralization. Metan1orphic mineral assemblages indicate that upper greenschist to middle amphibolite facies conditions were attained. Geological and geochenucal evidence indicates that the Central Metavolcanic Belt evolved in an island arc environment. Metavolcanic rocks from both the Waddy and Star Lakes areas display similar characteristics on variation diagrams (e.g. AFM and the Jensen cation plot) in that the dominant trend is calc-alkaline with some basic to intermediate types having a mildly tholeiitic character. A few samples from the southern end of Lower Waddy lake display komatiitic to basaltic-komatiitic afl'injties. The relatively immobile minor and trace elements (e.g. Ti , Zr, Nb, Y, Cr) provide reliable characterization of the metavolcanics, particularly of the basalts, which have highly distinctive trace element properties. Geochemical patterns for the basalts are similar to those for modem volcanic arc basalts. Low initial 87Sr/86Sr ratios (0.7017 - 0.7019) are consistent with a subduction-related origin for the volcanics. The major plutons have chemical properties typical of volcanic arc granites and are largely calc-alkaline in character, showing little chemical variation from the volcanics.

Jan 1, 1986

By W. A. Alexander

Introduction In the course of a programme of research on beryllium in progress in these laboratories, knowledge of the recrystallization temperature became necessary. As the information is not available in the literature, the determination of this temperature for metallic beryllium was undertaken. By the reduction of grain size through working and recrystallization and the probable simultaneous induction of preferred orientation, it was hoped to improve the working properties of beryllium at lower temperatures. The recrystallization temperature is usually determined by observing the lowest temperature of annealing at which new crystals are formed in severely cold-worked metal or alloys. This temperature is profoundly influenced by the following factors: the purity of the metal, in the case of an element, or the composition of the alloy; the degree of straining or working; the temperature of straining; the original grain size; and the time held at the annealing temperature. The observed temperature is lowered by higher purity, more severe straining, lower temperature of working, smaller original grain size, and longer time of annealing. Beryllium presents special difficulties in that the percent elongation in tension is effectively zero, so that ordinary squeezing or rolling was not possible. A possible means of straining was suggested by the fact that indentation hardness tests could be made. It was known from earlier work that the metal could be worked at elevated temperatures, so that working at the lowest feasible temperature and quenching might also be a means of producing strain. The purity of the metal is also a point of some uncertainty in the case of beryllium. Losano has prepared 99.96% Be which appears to be the best reported. Distilled metal used in the present work approached this purity. However, by analogy with other metals, residual impurities may have a pronounced effect on the recrystallization. Further purification of beryllium would evidently entail considerable difficulties due to the highly reactive nature of the metal, and was not attempted.

Jan 1, 1947

By Narasimha Mangadoddy, Balraju Vadlakonda

"Bubble size distribution, bubble rise velocity and gas and solids hold-up are the key major hydrodynamic parameters that are extensively used for column flotation design and performance evaluation. The distribution characteristics of mean gas hold-up is studied using electrical resistance tomography (ERT) coupled with pressure transducers (PT) in column flotation. The ERT technique facilitates non-invasive and nonintrusive visualization of different flow regimes even in the presence of particles in a column flotation. The effect of superficial gas velocity, feed flow rate and slurry height in the column on mean gas hold-up and its radial distribution has been analysed for both two-phase and three phase flows. Experimental results show ERT coupled with PT is suitable as an online monitoring tool to provide useful information on the three-phase flow hydrodynamic parameters of the column flotation. The tomography images, which were generated using a modified sensitivity back projection algorithm, are employed to explore the influence of parameters in two phase flow in column flotation. Mean gas and solids hold-up values extracted from ERT have been critically analysed for the column operating in various flow regimes. Gas hold-ups and solid hold-ups results using ERT are in very good agreement with conventional estimation and correlations obtained using pressure transmitter methods. Meanwhile, the results show that the gas hold-ups in the centre region increase constantly with an increase in the superficial gas velocity, whereas solid hold-ups distribution is very heterogeneous for high gas velocity. Furthermore, the results also indicate that ERT is a very powerful tool for diagnosing the 'inside' flow behaviour of gas –liquid–solid three phase flow in columns operating for a wide range of flow regimes.INTRODUCTIONColumn flotation is perhaps the most significant technological innovation in flotation machinery and its successful introduction in mineral processing plants. There has been a lot of attention in understanding the various mechanisms that take place during operation. Due to many reasons column flotation has been found to yield better performance than conventional flotation cells, particularly with fine particles (Honaker & Mohanty, 1996). Due to complex flow behavior in nature, the performance of column flotation influenced by on flow characteristics of the process, (Jena, Biswal, Das, & Reddy, 2008). Previously basic research is carried out to evaluate the effect of the hydrodynamic parameters on performance of column flotation (Finch, J.A.;Dobby, 1991). Many techniques have been developed that could be used to experimentally analyse the hydrodynamics of column flotation. Tomography techniques are well sound to investigate the hydrodynamics for process equipment. Among that, Electrical resistance tomography (ERT) has been used in various industrial investigations for visualization of the concentration profiles and characteristics of the fluid dynamics in gas–liquid two-phase systems (Wang, Dickin, & Mann, 1999; Williams, R.A; Wang, 2000). ERT is an imaging technique to analyse the internal flow behavior non-intrusively. ERT provide very useful tools for measuring and monitoring of column flotation process on line. Due to its high speed capability, low cost measurement, robust sensors, ERT is considered to be the most powerful tool among other tomography techniques such as positron emission tomography (PET), magnetic resonance imaging (MRI), optical and infrared tomography. Application of ERT has extended in process systems due to its improved speed of data acquisition, sensitivity, flexibility and noise immunity. In multiphase flow of bubble columns, gas hold-up and solid hold-up are explored by using the coupling of ERT and difference pressure method (Jin, Han, Yang, & He, 2010)."

Jan 1, 2016

By V. K. Karra

"A simplistic algorithm jar simulating the rod or ball mill Bond grindability test applied to ores and minerals is presented. A performance comparison between the present algorithm and a previously published algorithm by Kapurot, modified in this work jar a fair evaluation, is also given. A worked example is furnished jar leading the reader through the various calculations.IntroductionThe Bond grindability test is widely used for the prediction of the power requirement of an industrial grinding mill. The procedures for conducting this test in either a ball or a rod mill are available(1). In the case of a ball mill, batch grind abilities have been correlated to Bond grindabilities to help monitor day-today variations in ore grindability for the purpose of plant control( 2,3). Of special interest is the algorithm presented by Kapur(3) for the simulation of the Bond test. In practice, the test lasts from 6 to 14 cycles (4 to 10 hours). With this algorithm, one can predict the Bond grind ability using information available from only the first two cycles.Sometimes the prepared feed for the grindability test contains too much fines compared to the total product desired at the mesh of grind under consideration. In such a case, the operator separates the fines from the test feed and adds to the remaining coarse fraction an equal amount of fresh feed. This combined feed then forms the feed to the first cycle of the test. In the present work, Kapur&apos;s algorithm is modified to include this special case. A new and relatively simpler algorithm is also presented. Statistical equations relating work index to pertinent variables are also given."

Jan 1, 1981