What is a good online or offline complete reference for mathematics?

Im trying to learn graduate level math along with quantum physics mostly using youtube courses and open source text books. For solving problems and working out the math involved in quantum physics etc, it would be great if there was a searchable reference I could use to find axioms, theorems, concepts, symbols, formulas, functions, rules, identities, properties of mathematical objects etc all in one place. Preferably offline but inline would do as well.

I dont want to keep using gpt to ask for definitions, and wikipedia appears to be incomplete. For example the wikipedia page for outer product (https://en.wikipedia.org/wiki/Outer_product) does not address complex vectors.