Hansen, Harry L., author
Richard D. Irwin, 1956
Buku Teks
Narver, John C., author
Holt, Rinehart and Winston, 1971
Buku Teks
Morris, Michael H., author
Sage, 2001
Buku Teks
Clark, Fred E.
MacMillan Co., 1931
Buku Teks
edited by Philip R. Cateora and Lee Richardson
Appleton-Century-Crofts, 1967
Buku Teks