Oxford University Press, 1979
Buku Teks
Malecki, Edward J.
Longman Scientific & Technical, 1991
Buku Teks
edited by Anne Hellum, Henriette Sinding Aasen
Cambridge University Press, 2013
Buku Teks
Jayawickrama, Nihal
Cambridge University Press, 2017
eBooks
Langley, Anne
Chandos Publishing, 2006
Buku Teks SO