Halpern, Joel M.
Prentice-Hall, 1967
Buku Teks SO
Forman, Harrison
Crown Publisher, 1948
Buku Teks SO
Artikel Jurnal
E. Aminudin Aziz
Indonesia University of Education. Faculty of Language and Art Education, 2005
Artikel Jurnal
Parish, William L.
University of Chicago Press, 1978
Buku Teks SO