Drasgow, F. (1986), “Polychoric and Polyserial Correlations,” in S. Kotz, N. L. Johnson, and C. B. Read, eds., Encyclopedia of Statistical Sciences, volume 7, 68–74, New York: John Wiley & Sons.

Olsson, U. (1979), “Maximum Likelihood Estimation of the Polychoric Correlation Coefficient,” Psychometrika, 12, 443–460.