Driver, Harold E.
Mouton Indiana University 1963
Buku Teks
Schwartzman, Helen B., author
Sage Publications, 1993
Buku Teks
Donnelly, Thomas C.
The University of New mexico Press, 1953
Buku Teks
Pick, James B., author
Westview , 1989
Buku Referensi
Dullemen, Inez van, author
Querido, 1988
Buku Teks