Laws, Valerie
Buku Teks
Tippens, Paul E.
McGraw-Hill, 1983
Buku Teks
Washington, Allyn J.
Pearson - Prentice Hall, 2009
Buku Teks SO
Clynes, A.J.
International Development Program of Australian Universities, 1985
Buku Teks
Smith, Jennifer
Macmillan, 1982
Buku Teks