edited by Noel Entwistle
Routledge, 1990
Buku Referensi
edited by David C. Berliner and Robert C. Calfee
MacMillan Library Reference USA, 1996
Buku Referensi
Guth, Hans P., author
Wadsworth, 1969
Buku Teks
edited by. David H. Jonassen
MacMillan Library Reference USA, 1996
Buku Referensi
Morphet, Edgar L. (Edgar Leroy), 1895- , author
Prentice-Hall, 1982
Buku Teks