Soth, Lauren
Thomas J. Crowell, 1965
Buku Teks
Wilcox, Walter W., author
Prentice-Hall, 1951
Buku Teks
Schultz, Theodore W., author
McGraw-Hill, 1953
Buku Teks
Gates, Paul W., author
Holt, Rinehart and Winston, 1962
Buku Teks
Cochrane, Willard W., author
University of Minnesota Press, 1964
Buku Teks