London : Hamish Hamilton Ltd
Majalah, Jurnal, Buletin
Artikel Jurnal
Wardlaw, Gordon M., 1912-1989
McGraw-Hill, 2004
Buku Teks SO
R.S. Jassal, Joint Secretary, External Publicity Division,
Majalah, Jurnal, Buletin
edited by E.C. Cuff; G.C.F. Payne
George Allen and Unwin, 1984
Buku Teks SO