Purdy, G.A., author
Copp Clark, 1958
Buku Teks
Hole, Frank, author
Holt Renehart and Winston, 1966
Buku Teks
editor, Truman Simanjuntak
Gadjah Mada University Press, 2002
Buku Teks
U. S. Congress Office of Technology Assessment, 1986
Buku Teks
Kuhn, Herbert, author
Random House, 1955
Buku Teks