Artikel Jurnal
Smith, T. Lynn
J. B. Lippincott Company, 1960
Buku Teks
United Nations Fund for Population Activities, 1985
Buku Teks
Zopf, Paul E,Jr
Mayfield Publishing, 1984
Buku Teks
edited by John F. Kantner, Lee McCaffrey
Lexington Books, 1975
Buku Referensi