Tibbetts, A.M.
Scott, Foresman and Company, 1979
Buku Teks
Winterowd, W. Ross
Harcourt Brace Jovanovich, 1981
Buku Teks
Jordan, John E.
Harper & Row, Publishers, 1965
Buku Teks
Winterowd, W. Ross
Holt, Rinehart and Winston, 1968
Buku Teks
Smith, Wiliam F.
Harcourt Brace Jovanovich, Inc., 1983
Buku Teks