Gant, George F.
University of Wisconsin Press, 1979
Buku Teks
Todaro, Michael P.
Longman, 1997
Buku Teks
Todaro, Michael P.
Addison-Wesley , 2000
Buku Teks
Todaro, Michael P.
Addison-Wesley , 2000
Buku Teks
Griffin, Keith
St. Martin Press, 1989
Buku Teks