Cameron, Peter J., Introduction to Algebra, 2nd ed (New York: Oxford University Press, 2008), Oxford mathematics <http://ezproxy.library.qmul.ac.uk/login?url=http://www.vlebooks.com/vleweb/product/openreader?id=QMUL&isbn=9780191566226&uid=^u>
Ledermann, Walter and Weir, Alan J., Introduction to Group Theory, 2nd ed (Harlow: Longman, 1996), Longman mathematics series