Washington U.S. Department of Health, Education, and Welfare 1955
Buku Teks
Board of Trusless, 1960
Buku Referensi
edited by Marvin Farber
University of Buffalo, 1950
Buku Teks SO
Whitaker,Arthur P.
Harvard University Press, 1948
Buku Teks
The America University, [date of publication not identified]
Buku Teks