Rienow, Robert
D.C.Heath and Company, 1958
Buku Teks
Babcock, Chester D., author
Scott, Foresman, 1956
Buku Teks
Farley, John E., author
Prentice-Hall, 1987
Buku Teks
Cuber, John F
Henry Holt And Company, 1951
Buku Teks
Shostak, Arthur B.
Macmillan Publishing Company, 1974
Buku Teks