The list of MathSciNet publications that mention categories or functors established by Peter Freyd is most interesting. May I point to 2 important papers by Charles Ehresmann in this period which, though not using the word "category", might also be relevant since they extensively use "groupoids" (i.e., categories in which all the morphisms are invertible) and are at the root of a large part of the subsequent work on categories done by and around Charles in the sixties? I don't have access to the MathSciNet reference, but it should be easy to find. 1. Les prolongements d'une variete differentiable, Atti IV Congresso Unione Matematica Italiana, Taormina (1951), 1-9. In this paper Charles defines what will be later called "the category of infinitesimal jets" (between differentiable manifolds), with its domain, codomain and composition maps, but without using the name category (he said to me that he did not know of categories at this date). And he explicitly mentions that the invertible jets form a groupoid. 2. Les prolongements d'un espace fibre differentiable, C.R.A.S. Paris, 240(1955 ), 1755-1757. Here Charles defines the action of a groupoid on a set and its associated "principal groupoid" as a generalization of the fibre bundle theory. he had developed in the fourties. He also considers the topological and differentiable cases, thus giving the first definition of an "internal" groupoid and groupoid action. He applies this to study the prolongations of manifolds. His 1957 paper on categories (cited in the list) is a direct sequel of this paper, except that the groupoids are then replaced by categories. And the internal case has led in 1963 to his extensive study of internal categories and category actions (he used then the term "structured" instead of "internal"). With my best wishes for all Andree C. Ehresmann 13-Jan-2002 19:35:24 -0400,3660;000000000001-00000000