His main interest lyed in General Equilibrium Theory and its reformulation for planning purposes. Along this line we may classify his dissertation (1966), directed toward the problem of the possibility of actually computing a solution to the general equilibrium model. At the time it was not known that such a solution exists if and only if a certain transformation has a fixed point, so that the equilibrium problem is logically equivalent to the determination of such fixed points; this follows from more recent work in which he has also contributed. Therefore the task he had set of proving the existence of equilibrium without fixed point theorems was hopeless. Nevertheless, the proof he devised contained the elements for the actual computation of a solution of the model to any degree of accuracy, measured in terms of deviation of demand from supply. A different proposal for computing such solutions is contained in his article on "The welfare adjustment process ..." (1971), but there one is not sure to obtain the solution in every case.

Problems of efficiency in a growing competitive economy are analyzed in "Competencia perfecta y eficiencia ..." (1973), whereas the effects of explicitly introducing the government with its tax powers into the picture were explored in "Política tributaria ..." (1970). Finally, under the category of publications referring to the analysis of the general equilibrium model, especially in reference to the chapter on demand theory, we can mention "On the characterization of aggregate excess demand" (1974), "A characterization of community excess demand functions", (1974, in collaboration), "Homothetic preferences and community excess demand functions", (1976), and "Implications of Microeconomic Theory for community excess demand functions" (1977). All refer to the Sonnenschein conjecture that continuity and Walras's Law are the only empirical implications of the usual textbook assumptions of consumer theory. The last publication mentioned provides a survey of the subject.

A different line of research is exemplified by "Criterios de desarrollo económico óptimo" (1968) and "On the utility of infinite programs ..." (1971) but remains as yet mainly unpublished except as mimeographed notes of the Cowles Foundation (1967) {ESTO ESTA OUTDATED}. It refers to the structure of preference over time, following ideas originating with Irwing Fisher and Tjalling C. Koopmans, and the application of special assumptions on preferences such as stationarity and limited complementarity on the determination of optimal consumption programs.

In "Economic Integration, income distribution, and consumption ..." (1975), jointly with Ana María Martirena-Mantel, he developed a new rationales for economic integration with the aim of overcoming a well known and basic dilemma in the theory of international economic integration (custom unions). This study finds out, among several other outcomes, that when evaluating the pure integration benefits from a non-cooperative initial point, the free trade position remains outside the contract curve, i.e. it is not optimal to reduce to zero all tarkff barriers to international trade among member countries.

Outgrowth from problems analyzed in his course on the Theory of Economic Policy are "Políticas de estabilización económica" (1971) and "efectos de la política de tasas de interés ..." (1972), the first on stabilization policy, and the second on interest rate policy.

Another line of research studies the general equilibrium model from the point of view of the utility possibilities it allows to the participants of the market game. Different aspects referred to the representation of markets by convex utility possibility sets are referred to in my dissertation, in "Representation of preferences by concave utility functions" (1969, unpublished), and in "Non-convexifiable Pareto sets" (1978, with Yakar Kannai). The solution of the model corresponding to a competitive equilibrium has been analyzed in "Optimos de bienestar inducidos por el mercado" (1976), "The linear exchange model and induced welfare optima" (1976, mimeo, Cowled Foundation), and "Equilibrio y optimalidad en economias de intercambio lineales" (1978).

Last, but not least, I would like to mention my interest in putting all these theoretical constructs to work in an application to the Argentine economy. Bits and pieces appear mainly in unpublished work, as in "Un modelo neoclásico de integración económica" (1965, Instituto Di Tella, mimeo), "Modelo de corto plazo" (1971, mimeo, Secretaría del CONADE), and "La utilización de modelos formales para la planificación económica" (1978). Also the computational methods have been developed, as in "An efficient algorithm for the computation of a solution to von Neumann's model" (1969, mimeo, Instituto Di Tella), and "Un algoritmo acelerado para la determinación de una solución de equilibrio económico" (1978, Banco Central de la República Argentina). Most of these investigations are still unfinished, pending continuing access to computing facilities, difficult to obtain in Buenos Aires, but which will partly be solved next year with the acquisition of a small computer by the Di Tella institute.