Lawrence L. Bethel ... [et al.]
McGraw-Hill, 1954
Buku Teks
Seckler-Hudson, Catheryn, author
Washington, D.C., The American University Press
Buku Teks
Anthony, Robert N. (Robert Newton), 1916-2006, author
Harvard University, 1952
Buku Teks
Brown, Wilfred
Heinemann, 1971
Buku Teks
McNulty, James E., author
University of Pennsylvania Press, 1964
Buku Teks