Dacey, Austin, 1972-
Brown & Benchmark, 1994
Buku Teks SO
Schneider, Susan C.
Prentice-Hall, 1997
Buku Teks
Adams, Katherine H.
Mayfield Publishing Company, 2000
Buku Teks SO
Dacey, John S.
McGraw-Hill, 2002
Buku Teks SO
Gillespie, Sheena
Allyn and Bacon , 1994
Buku Teks SO