Is it okay to refer a chess product?

Question

I know that in stackoverflow, it's forbidden to share link to commercial products, because it's considered as advertising.

I would like to know if it's okay(not considered as advertising) to refer a chess product in chess.stackexchange.

I see some questions/answers are referring some books already, without penalization. But because of the policy of stackoverflow, I wanted to sure.

Thanks in advance.

Answer 1

It is allowed, as long as you disclose your affiliation with the product (if any):

The community here tends to vote down overt self-promotion and flag it as spam. Post good, relevant answers, and if some (but not all) happen to be about your product or website, that’s okay. However, you must disclose your affiliation in your answers.

From https://chess.stackexchange.com/help/promotion