Robequain, Charles, 1897-1963
Longmans, 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