What are good advanced textbooks to learn mathematics for economist? I am looking for books or other sources that focus on math that is above bachelor level (i.e. above just simple calculus). I am not looking for a specialized text for some field but just general mathematics at graduate level covering wide range of topic. My current math skills are very shaky after some simple univariate/multivariate calculus. If instead of textbook you know of good MOOC course that you could recommend it would help me as well. Thank you!
In my honest opinion the best book in this regard is fundamental methods of mathematical economics by Chiang and Wainwright.
It starts at the very basics and then goes all the way up to dynamic optimisation, also covering linear algebra, matrices, advanced calculus  topics such as implicit functions and equation solving at all levels.
Combined with a fine and clear step by step writing style and lots of examples and exercises I find it really a good book.