George Allen and Unwin, 1982
Buku Teks
Penniman, Howard R.
American Enterprise Institute for Public Policy Research, 1978
Buku Teks
Bowen, Howard R
Harper & Brothers, 1953
Buku Teks
Watson, Donald Stevenson, author
Houghton Miffiln, 1960
Buku Teks
Steiner, George A. (George Albert), 1912-, author
McGraw-Hill, 1953
Buku Teks