Kendrick, M. Slade
Houghton Mifflin , 1951
Buku Teks
Poole, Kenyon E.
N.Y. Rinehart , 1956
Buku Teks
Sharp, Ansel M.
Illinois Dorsey Press , 1964
Buku Teks
edited by Inge Kaul and Pedro Conceicao
Oxford University Press, 2006
Buku Teks
Foundation for Advanced Information and Research, 1992
Buku Teks