1. Heredity in human twinning
2. (1983): Occupational Mortality in Washington State 1950–1979 DHEW, National Institute for Occupational Safety and Health, Publication No. (NIOSH) 76-175-A, B, C.
3. , , , (1970): “Statistical Package for the Social Sciences.” New York: McGraw Hill.
4. United States Bureau of the Census (1960): Classified Index of Occupations and Industries, 1960 Census of Population. Washington, DC, U. S. Government Printing Office.