Marion Wesley Todd
Macmillan, 1934
Buku Teks
Hyman, Herbert H., author
John Wiley & Sons, 1972
Buku Teks
Artikel Jurnal
Fink, Arlene, author
Thousand Oaks : SAGE PUBLIKATION, 2003,
Buku Referensi
Fink, Arlene, author
Thousand Oaks : SAGE PUBLIKATION, 2003,
Buku Referensi