Stewart, Douglas
Angus & Robertson, 1966
Buku Teks SO
Cornell University Press, 1950
Buku Teks SO
Maclennan, Hugh
Macmillan Co. , 1945
Buku Teks SO
Thomas, Hugh
Harper & Row, 1967.
Buku Teks SO
Davies, Hugh Sykes
Published for the British Council by Longmans, Green, 1960
Buku Teks SO