Bursk, Edward Collins, author
Cambridge, Mass, Harvard University Press
Buku Teks
Bower, Marvin
Massachutts Harvard University Press , 1949
Buku Teks
Jones, Manley Howe
Ill Irwin , 1957
Buku Teks
Chambers, John Carlton, 1928-, author
John Wiley & Sons, 1974
Buku Teks
Arnold, John D., author
McGraw-Hill, 1981
Buku Teks