Evans, G.O., author
Taylor and Francis, 2009
Buku Teks
George Routledge and Sons, 1969
Buku Referensi
Treadwell, F.P., author
John Wiley & Sons, 1963
Buku Teks
Raffles, Thomas Stamford, author
Oxford University Press, 1982
Buku Referensi
Radhakrishnan, S. (Sarvepalli), 1888-1975, author
Macmillan, 1951
Buku Teks