This helped me a lot to understand quaternions using simple algebra: https://math.stackexchange.com/questions/147166/does-my-definition-of-double-complex-nonco

This helped me a lot to understand quaternions using simple algebra: https://math.stackexchange.com/questions/147166/does-my-definition-of-double-complex-noncommutative-numbers-make-any-sense https://math.stackexchange.com/questions/147166/does-my-defi...