I haven't tried this site myself, but it looks helpful: https://netmath.illinois.edu https://netmath.illinois.edu My short book on this in case you want to go

I haven't tried this site myself, but it looks helpful: https://netmath.illinois.edu https://netmath.illinois.edu My short book on this in case you want to go farther: https://read.amazon.com/kp/embed?asin=B01N2XC56E&preview=newtab&linkCode=kpe&ref_=cm_sw_r_kb_dp_HTtyybGDRR86E https://read.amazon.com/kp/embed?asin=B01N2XC56E&preview=new...