Gregg, Pauline
George G. Harrap, 1967
Buku Teks SO
A.G. Champion...[et al.]
Baltimore, Md., USA: Arnold, 1987
Buku Teks SO
Clapham, John, Sir
The Cambridge University Press, 1949
Buku Teks SO
edited by F. M. L. Thomson
Cambridge University Press, 1990
Buku Teks SO
edited by F. M. L. Thomson
Cambridge University Press, 1990
Buku Teks SO