Friedmann, Wolfgang, 1907-1972, author
Penguin Books, 1972
Buku Teks
Shaker Verlag, 2003
Majalah, Jurnal, Buletin
Westview Press, 1978
Buku Teks
edited by Maureen Baker
McGraw-Hill Ryerson, 1984
Buku Teks
Forman, Harrison
Crown Publisher, 1948
Buku Teks