DeCarvalho, Roy Jose
Praeger , 1991
Buku Teks SO
Tageson, C. William
Dorsey Press, 1982
Buku Teks SO
editor, Kirk J. Schneider, James F.T. Bugental, J. Fraser Pierson
Sage Publications, 2001
Buku Referensi
Kirk J. Schneider, J. Fraser Pierson, James F.T. Bugental, editor
Sage Publications, 2001
Buku Teks SO
Williams, Gardner
Philosophical Library, 1951
Buku Teks SO