edited by David C. Berliner and Robert C. Calfee
Macmillan Library Reference, 1996
Buku Referensi
Guth, Hans P.
Wadsworth, 1969
Buku Teks SO
edited by. David H. Jonassen
Macmillan Library Reference, 1996
Buku Referensi
Morphet, Edgar L. [Edgar Leroy], 1895-
Prentice-Hall, 1982
Buku Teks
Shepherd, Elizabeth J., 1960-
Facet Publishing, 2003
Buku Referensi