I am writing book with a lot of math formulas. I am interested to print them correctly according to typography rules, Knuth's recommendations or AMS-society's recommendations.
I saw in this question and here some interesting points and even reference for this book, which doesn't work for me for some reason.
From this point I started to think of rules where I should help TeX to make correct spacing, fonts, symbols, formatting and etc. in math formulas. I mean where I should manually help TeX. I don't want break cases, where TeX makes it automatically, for example, \sin x makes correct spacing, fonts without my \, \; \! \quad, etc.
for example, AMS-society recommends to print \int f(x)\,dx instead of \int f(x)dx.
Here is the question. Where can I get list of recommendations or can someone provide cool book or answer with format rules for formulas where LaTeX doesn't make all work? All resources in the Internet refer to that site, but I can't access it.
Sorry, if duplicate, off-topic or something else.
Currently, I've found these rules and make a small list according to SE and books (I hope I will update them for me as my book will be edited more):

\ratio{x:y:z} = \ratio{3:4:5},\map{f: A \to B},\forall x \in A \suchthat f(x) = 12,\set{ x : 1 < x < 2 }or\set{ x \given 1 < x < 2}or\set{ x \suchthat 1 < x < 2},\int f(x) \d x. – Manuel Sep 21 '17 at 14:01