Shultz, Richard D.
Harper & Row Pub., 1985
Buku Teks
Davis, Richard A.
Wm.C. Brown Publishers, 1996
Buku Teks
Graham, Archie Richard
Prentice-Hall, 1975
Buku Teks
Romanek, Richard J.
Prentice-Hall, 1975
Buku Teks
Farmer, Richard N., author
Belmont, Cal. Wadsworth 1969,
Buku Teks