I was wrong, it was on Stackexchange. Stackexchange is full of true gems, and they really often have no or only very few upvotes, because nobody recognizes thei

I was wrong, it was on Stackexchange. Stackexchange is full of true gems, and they really often have no or only very few upvotes, because nobody recognizes their value. https://math.stackexchange.com/a/952050 https://math.stackexchange.com/a/952050