1. Gunning, R. (1952) The Technique of Clear Writing. McGraw-Hill, pp. 36-37.
2. A new readability yardstick;Flesch;Journal of Applied Psychology 32 (3),1948
3. Simplification of Flesch Reading Ease Formula;Farr;Journal of Applied Psychology 35 (5),1951
4. Readability formulas: Useful or useless;McClure;(an interview with J Peter Kincaid) IEEE Transactions on Professional Communication 30,1987
5. Computer Readability Editing System;Kincaid;IEEE Transactions on Professional Communication 24 (1),1981