edited by Peter Burke
Pennsylvania State University Press, 1995
Buku Teks SO
Fedrizzi, Mariann
South Western Cengage Learning, 2011
Buku Teks SO
Longman , 1999
Buku Teks SO
MIT Press, 1977
Buku Teks
edited by Lesley Brown
Clarendon Press, 1993
Buku Referensi