[Canberra] Angus & Robertson 1989,
Buku Referensi
Daniel, Hawthorne
G.P. Putnam's Sons , 1943
Buku Teks SO
Oliver, Douglas L.
Harvard University Press, 1951
Buku Teks SO
Oliver, Douglas L.
Harvard University Press, 1958.
Buku Teks SO
Campbell, I.C.
University of Queensland Press, 1989
Buku Teks SO