Pertti J, Pelto, author
Cambridge University Press, 2012
eBooks
Pelto, Pertti J.
Harper & Row, Publishers, 1970
Buku Teks
Pelto, Pertti J.
Cambridge University press, 1978
Buku Teks
Jenks, Albert Ernest
American Association, 1937
Buku Teks
McGee, R. Jon, author
McGraw-Hill, 2012
Buku Referensi