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