Are there open introductory materials in English for QA?

Question

Software testing

Good afternoon.

One of my colleagues is engaged in testing, and wants to improve the theory of QA (he knows the business inside and out). I ask for advice in the selection of material.

Ideally, something "for dummies", then something introductory.

Restriction: English only (the only common language).
Availability (read, free) is desirable, but not critical.
The format is not critical: a series of posts, a book, a recording of a conference, video lectures - everything will do.

Answer 1

Based on the results of surveys / google, I prepared a small shortlist.
1. Comrade Kaner . I used it to get acquainted with QA 5 years ago, but it is relevant even now. As one of the comrades noted, "I read the channel about 12 years ago and yes it is relevant)".
2. ISTQB A bunch of .pdf categorized by topic and skill level.
3. Old (2014) list of books. Includes, among other things, texts in Russian, and books on "non-core" topics.
I hope you find the catalog helpful.
Good luck.