1. Principles of Economics;Marshall,1920
2. C. Babbage, On the Economy of Machinery and Manufactures, fourth ed., John Murray, London, quoted in G.M. Hodgson, (1993) Economics and Evolution, Univ. of Michigan Press, Ann Arbor., 1946, p. 115.
3. C. Leslie, The Known and the Unknown in the Economic World, (Original work published). Fortnightly Review. Reprinted from: Essays in Political Economy. (1888), Longmans, Green & Co., London, 1879, pp. 221–242.
4. The market for “Lemons”;Akerlof;Quarterly J. Econo.,1970
5. Market Signalling;Spencer,1977