Bogart, Leo ed
Markham Company, 1969
Buku Teks
Clark, Fred E.
Macmillan, 1947
Buku Teks
Clark, Fred E.
MacMillan Co., 1931
Buku Teks
Converse, Paul Dulaney, 1889-, author
Prentice-Hall, 1958
Buku Teks
edited by Reavis Cox and Wroe Alderson
Richard D. Irwin, 1950
Buku Teks