Burns, Arthur Edward, author
Harcourt, Brace, 1948
Buku Klasik
general editor, David W. Pearce
Macmillan Reference Books, 1989
Buku Referensi
Ehrenberg, Ronald G., author
Pearsons Addison-Wesley , 2009
Buku Teks
general editor, David W. Pearce
Macmillan Press, 1992
Buku Referensi
Schiller, Bradley R., author
McGraw-Hill, Irwin, 2005
Buku Teks