Portune, Robert
W.H. Anderson, 1971
Buku Teks
edited by Donald H. Shively
Princeton University Press, 1971
Buku Teks SO
edited Carmen Blacker [and others]
Princeton University Press, 1971
Buku Teks SO
Artikel Jurnal
International Society for Educational Information
ISEI, 1987
Buku Teks