1. R. I. DawsonAn unpublished study made at the Equitable Life Assurance Society, 1957 .
2. C. R. Langmuir(Psychological Corporation) Personal communication to authors, 1960 .
3. W. G. Mollenkopf"The Logical Analysis Device as a Predictor of Programming Skill ." An unpublished study made at Procter & Gamble, 1960 .