I took notes.
When SH3 first came out, I went to the library and checked out (and read) all the books on U-Boats. When SH4 came out, I did the same thing. Concurrently, I also read here, at the forum, a number of "assumptions" about what fleet boats could and could not do. Many of the assumptions were B.S. and, as the B.S. got to the point where guys were demanding changes to reflect their uninformed assumptions, I (and others ... RR, for example) started posting facts. Naturally, facts require proof. So I provided quotes from the books.
Unfortunately, some of the same assumptions came up time and time again. Along with the demands to change SH4. So, since the books belong to the library (and I don't care to go running back to the library and re-read a book every time I need a quote), I wrote down the page numbers.