Ehrenfeld, Michael
AO Foundation, 2012
Buku Teks
edited by Roy Freedle
N.J. L. Erlbaum Associates, 1990
Buku Teks
Pintner, Rudolf, 1884-1942
Henry Holt and Company, [1927]
Buku Teks
by Robert K. Lindsay [and others]
McGraw-Hill, 1980
Buku Teks
Springer, 2012
eBooks