Liebeck, M. W. A Concise Introduction to Pure Mathematics. Fourth edition. Chapman Hall/CRC mathematics. Boca Raton: CRC Press, Taylor & Francis Group, 2016. Web. <http://eu.alma.exlibrisgroup.com/view/action/uresolver.do?operation=resolveService&package_service_id=3039389150002418&institutionId=2418&customerId=2415>.