Gellhorn, Walter, author
Macmillan, 1961
Buku Teks
Mendelson, Wallace, author
Dorsey Press, 1980
Buku Teks
Jensen, Merrill, author
Kriger, 1979
Buku Teks
Bartholomew, Paul C., author
W.M.C. Brown, 1951
Buku Teks
edited by Robert A. Goldwin and William A. Schambra
American Enterprise Institute for Public Policy Research, 1985
Buku Teks