Cameron, Peter J. (2008). Introduction to algebra: Vol. Oxford mathematics (2nd ed). Oxford University Press. http://ezproxy.library.qmul.ac.uk/login?url=http://www.vlebooks.com/vleweb/product/openreader?id=QMUL&isbn=9780191566226&uid=^u
Ledermann, Walter & Weir, Alan J. (1996). Introduction to group theory: Vol. Longman mathematics series (2nd ed). Longman.