Prabhu, Anjali
Wiley Blackwell, 2014
Buku Teks
edited by I. William Zartman and William Mark Habeeb
Westerview Press, 1993
Buku Teks
Murdock, George Peter
McGraw-Hill, 1959
Buku Teks
Murdock, George Peter
McGraw-Hill, 1959
Buku Teks
Nielsen, Waldemar A.
Atheneum, 1966
Buku Teks