Richards, R. Malcolm
Scott, Foresman, 1984
Buku Teks SO
Unger, Maurice A.
Allyn and Bacon, 1969
Buku Teks SO
Garman, E. Thomas
Houghton Miffiln, 1985
Buku Teks SO
Kapoor, Jack R., 1937-
McGraw-Hill/Irwin, 2004
Buku Teks SO
Oxford University Press, 1993
Buku Referensi