1. The measurement of mental ability of “backward children;Abelson;“British Journal of Psychology,1911
2. Some experimental results in the correlation of mental abilities;Brown;British Journal of Psychology,1910
3. The effects of “observational errors” and other factors upon correlation coefficients in psychology;Brown;British Journal of Psychology,1913
4. Coefficient alpha and the internal structure of tests;Cronbach;Psychometrika,1951