Mulgan, John
Clarendon Press, 1967
Buku Teks SO
Harrap Book Limited, 1991
Buku Referensi
edited by Lesley Brown
Clarendon Press, 1993
Buku Referensi
by Herbert Barrows [and others]; under the general editorship of Gordon N. Ray
Houghton Miffiln, 1959
Buku Teks SO
edited by Louis G. Locke, William M. Gibson, George W. Arms
Holt, Rinehart and Winston, 1959
Buku Teks SO