Sharma, R.P., author
Sterling Publishers Private, 1984
Buku Teks
Joad, C.E.M., author
Clarendon Press, 1959
Buku Teks
edited by Joseph S. Roucek
Littlefield, Adams , !964
Buku Teks
edited David Marsh and Gerry Stoker
Macmillan, 1995
Buku Teks
Dyke, Vernon van, author
Stanford University Press, 1962
Buku Teks