At @whuber: stats.stackexchange.com/questions/423280 Come on, put it as a wiki. We need to help people.

Hmm.. I can see how this will lead to a discussion. You are/were correct.

@usεr11852 I share your instinctive feelings about helping, but we're not here to answer just any questions anybody feels like posting. (That's for this chat room. :-) On our site we have clear criteria for questions and this one doesn't meet them. Moreover, it's highly likely that if this question were made more specific, it would be identical to the others that ask similar questions.

@RScrlli: Strictly speaking, if you do not NEED "additional Maths" but rather to be admitted to a PhD programme. Especially as will take additional classes and you will be able to hone your abilities there. How are you expected to be prove your mathematical competency?

@whuber: Agreed.

@usεr11852 Actually I've been already admitted in the program, it's more of a personal thing, I wanted to be prepared to follow the courses of Functional Analysis and malliavin calculus

@whuber If I am honest with we I wasn't aware of the existence of this chat!

@RScrlli Understandable--glad you found it; and welcome!

Did you get any useful information from the search link I posted above?

@whuber I 've been reading some of the questions in the link and indeed, some of them were useful, as far as I saw the books I've been reading seem to be a good base, at least for the first courses I'll be following. Some doubts regarding the usefulness of some of the chapters still remain, but in any case I think I'll cover them just for personal pleasure. Thanks!

@RScrlli A requirement for my BA in math was passing an oral examination in linear algebra. The textbook was extremely abstract and non-numerical in orientation: it focused on concepts and generalities. That study served us all well no matter what we went on to do. I have always felt that this foundation was superior to the numerical or computational or matrix-oriented linear algebra courses frequently taught.

If your experience with linear algebra is primarily row-reduction and diagonalization, it might be worth looking into getting a stronger foundation. It certainly can't hurt... .

@whuber, what book was it?

Roger Godement, Algebra. I'm not necessarily recommending it, because after 50 years there must now exist more modern treatments, but it has worn well with time.