New York University Press, 1951
Buku Teks
Gallagher, Michael
McGraw-Hill, 2011
Buku Teks
Sage Publications, 2004
Buku Teks
Freymond, Jacques
Frederick A. Preager, 1964
Buku Teks
edited by V.A.C. Gatrell, Bruce Lenman, and Geoffrey Parker
Europa Publications, 1980
Buku Referensi