Robequain, Charles, 1897-1963
Longman, 1959
Buku Teks SO
Robinson, Danielm
Lonely Publications Pty Ltd, 2011
Buku Referensi
Mackinnon, John Ramsay
[Publisher not identified], [Date of publication not identified]
Buku Teks SO
Ali, Muhamad
Edinburgh University Press, 2016
eBooks
Groeneveldt, W.P. [Willem Pieter], 1841-1915
Bhratara, 1960
Buku Teks