Panchen, Alec L.
Cambridge University Press, 1994
Buku Teks
Odum, Howard T.
McGraw-Hill, 1981
Buku Teks
Niebuhr, Reinhold
Charles Scribners Sons, 1945
Buku Teks SO
Cornwell, Alan
McGraw-Hill, 1974
Buku Teks
Johnson, Kenneth D.
The Benjamin, 1984
Buku Teks