^Hans Eysenck, (1967). The biological basis of personality. Springfield, IL: Thomas.
^Hans Eysenck, (1991). Dimensions of personality: 16: 5 or 3? Criteria for a taxonomic paradigm. Personality and Individual Differences, 12, 773–790.
^
Saucier, G., & Goldberg, L. R. (1998). What is beyond the Big Five? Journal of Personality, 66, 495–524.
^
McCrae, R. R., & Costa, P. C., Jr. (1987). Validation of the five-factor model across instruments and observers. Journal of Personality and Social Psychology, 52, 81–90.
^
Costa, P. T., & McCrae, R. R. (1992). Four ways five factors are basic. Personality and Individual Differences, 13, 653–665.