Abercrombie, M. L. J.
[1960]  The Anatomy of Judgement, Penguin, Harmondsworth, 1979


Caws, Peter
[1965]  The Philosophy of Science, D. Van Nostrand, Princeton, New Jersey  [Chapter 6]


Copi, Irving M.
[1953]  Introduction to Logic, Macmillan, New York, Sixth Edition, 1982 [Chapter XII, § 7]


Hempel, Carl G.
[1965]  Aspects of Scientific Explanation, The Free Press, New York, 1970  [Chapter 6]


Kaplan, Abraham
[1964]  The Conduct of Inquiry. Methodology for Behavioral Science, Chandler Publishing Company, Scranton, Pennsylvania   [Chapter 2, § 6]


Madge, John
[1953]  The Tools of Social Science, Longmans, London, 1965


McLoughlin, J. Brian
[1969]  Urban and Regional Planning. A Systems Approach, Faber, London, 1973  [Chapter 7]


Rescher, Nicholas
[1979]  Cognitive Systematization, Basil Blackwell, Oxford  [Chapter XII]


Reynolds, Paul Davidson
[1971]  A Primer in Theory Construction, Macmillan Publishing Co., New York, 1986


Rorabacher, Louise E. with Georgia Dunbar and Clement Dunbar
[1988]  Assignments in Exposition, Harper & Row, New York, Ninth Edition  [Unit 11 : Classification]


Van Dalen, Deobold B.
[1962]  Understanding Educational Research. An Introduction, Mc-Graw-Hill Book Co., New York, 1979  [Chapter 2]