If you are from a non-technical background and you want to learn mathematics which could be helpful to you in your NLP or any other data science projects, then you can start learning from this site:
https://www.khanacademy.org/math.
If you want to access reference links, research papers, and books, then you can click on the following GitHub link:
https://github.com/jalajthanaki/NLPython/tree/master/Appendix2
If you want to add something to this page, then feel free to do so. Let's keep continuing this journey.