Towle, Joseph W.
Houghton Miffiln, 1965
Buku Teks
Calhoun, Richard P.
McGraw-Hill, 1958
Buku Teks
Kennedy, Jay
Longman Cheshire, 1994
Buku Teks
Johnson, Rossall James, 1917-
Richard D. Irwin, 1960.
Buku Teks
Knudson, Harry R., editor
SAddison-Wesley Pub. Co., 1967
Buku Teks