Bakke, Edward Wight, author
Charlew E. Merrill Books, 1963
Buku Teks
edited by Arthur M. Ross
University of California Press, 1965
Buku Teks
Levitan, Sar A., author
Harper & Row, 1982
Buku Teks
Jakubuskas, Edward B., author
Addison-Wesley, 1973
Buku Teks
Salant, Walter S., author
Brokkings Institute, 1961
Buku Teks