Pelto, Pertti J.
Harper & Row, Publishers, 1970
Buku Teks
Pelto, Pertti J.
Cambridge University press, 1978
Buku Teks
Pertti J, Pelto, author
Cambridge University Press, 2012
eBooks
Riedel, Marc
Garland Publishing Inc., 1993
Buku Teks
Dimen-Schein, Muriel, author
McGraw-Hill, 1977
Buku Teks