[1]
Croft, T. and Davison, R. 2020. Foundation maths. Pearson.
[2]
Elementary Algebra Textbook: http://mathrev.redwoods.edu/ElemAlgText/.
[3]
Mathematics Enhancement Programme: http://www.cimt.org.uk/projects/mepres/alevel/alevel.htm.
[4]
Underground Mathematics: https://undergroundmathematics.org/.