1. William Fellner’s Competition Among the Few, especially for its analysis of the counter-tendencies affecting the emergence of collusion, and Don Patinkin’s ‘Multi-Plant Firms, Cartels, and Imperfect Competition’ (Quarterly Journal of Economics, February 1947), for its analysis of entry phenomena under cartels. Much of the present analysis on the effects of the condition of entry on monopoly has grown out of this writer’s analysis in ‘A Note on Pricing in Monopoly and Oligopoly’ (American Economic Review, March 1949) and ‘Workable Competition in Oligopoly’ (ibid., May 1950).