# Lesson-resource links * [Variation theory](https://variationtheory.com/introduction/) * [Diagnostic questions](https://diagnosticquestions.com/) * [SSDD problems](https://ssddproblems.com/) * [Maths Venns](https://mathsvenns.com/) * [Delta Math](https://www.deltamath.com/) * [Classroom-Ready Rich Algebra Tasks](https://resources.corwin.com/classroomreadymath/algebrans) * [Open Middle Mathematics](https://www.openmiddle.com/) * [Custom Functions](http://natbanting.com/custom-functions/) * [Wanted parabola](https://chrishunter.ca/2019/01/08/wanted-parabola/) * [Menu Math](http://natbanting.com/menu-math/) * [Open-Up Resources](https://access.openupresources.org/curricula/our-hs-math) * [Citizen Math](https://www.citizenmath.com/lessons/explore-units/algebra-1)