Lang, Margaret
Routledge, 2001
Buku Teks SO
edited by Vic Barnett
John Wiley & Sons, 1981
Buku Teks SO
Gilbert, Joseph
Van Nostrand Reinhold, 1978
Buku Teks SO
Lang, Margaret
Routledge, 2001
Buku Teks SO
Anderson, Alan J.B.
Chapman and Hall , 1989
Buku Teks SO