Carroll, Alex, 1947-, author
Pearson Longman, 2007
Buku Teks
De Smith, S.A. (Stanley A.), author
Penguin Education, 1973
Buku Teks
Allen, Michael
Blackstone Press Ltd., s.a.
Buku Teks
Thompson, Brian
Blackstone press , 1997
Buku Teks
Phillips, O. Hood
Swett and Maxwell, 1973
Buku Teks