Croft, T., & Davison, R. (2020). Foundation maths (Seventh edition). Pearson. https://eu.alma.exlibrisgroup.com/view/action/uresolver.do?operation=resolveService&package_service_id=4841648670002418&institutionId=2418&customerId=2415
Elementary Algebra Textbook. (n.d.). http://mathrev.redwoods.edu/ElemAlgText/
Mathematics Enhancement Programme. (n.d.). http://www.cimt.org.uk/projects/mepres/alevel/alevel.htm
Underground Mathematics. (n.d.). https://undergroundmathematics.org/