Roscoe, Edwin Scott, author
Richard D. Irwin, 1959
Buku Teks
Woodward, Joan, author
Oxford University Press, 1965
Buku Teks
Lawrence L. Bethel ... [et al.]
McGraw-Hill, 1954
Buku Teks
Seckler-Hudson, Catheryn, author
Washington, D.C., The American University Press
Buku Teks
Brown, Wilfred
Heinemann, 1971
Buku Teks