Boren, Henry C.
D.C. Heath, 1977
Buku Referensi
Homo, Leon
Kegan Paul,Trench,Trubner & CO,LTD, 1927
Buku Teks
Jones, Mark Wilson
Yale University Press, 2000
Buku Teks
Nash, Ernest
Frederick A. Praeger, [1961-62]
Buku Referensi
Kebric, Robert B.
Mayfiled, 2000
Buku Teks SO