Rules about linking to external pages

Question

What are the rules about linking to external pages, which might be commercial?

For example I referenced The TeXBook and wanted to link to it, so that people who don't now it can find it better. The name is to close to "textbook" which confuses search pages. But what link would be acceptable? Can I link directly to Amazon, which might be understood as advertising (such links could include Amazon partner IDs to receive a commission) or only to Knuths website for it?

The same applies to other books and commercial software related to LaTeX. What would be still acceptable and whats not? Are there pre-defined rules from SE for this.

I thought I just bring this topic up for discussion.

Answer 1

For books, you could link to Wikipedia's “Book sources” page (at least if you know the ISBN). For the TeXBook this would be here. This page then has links to various online catalogs, libraries and book sellers.

For commercial software usually have a web site and I think it is fine to link there (as long as the software is relevant to the question, of course). Alternatively, you could link to Wikipedia.

Answer 2

The basic policy is in the FAQ:

May I promote products or websites I am affiliated with here?

Be careful, because the community frowns on overt self-promotion and tends to vote it down and flag it as spam. Post good, relevant answers, and if they happen to be about your product or website, so be it. However, you must disclose your affiliation in your answers. Also, if a huge percentage of your posts include a mention of your product or website, you're probably here for the wrong reasons. Our advertising rates are quite reasonable; contact our ad sales team for details. We also offer free vote-based advertising for open source projects.

I'd say it's pretty reasonable, and AFAIK we never had problems with this on TeX.SE.

Edit:

In relation to linking to books and other commercial resources -- I don't mind being referred to Amazon or other authoritative source where said books/manuals/software is available. I won't buy from there in a whim without seeing other options anyway. The only thing I'm against is when the submitter generates profit or other benefit for themselves through linking (affiliation programs, or advertising). Moderate promotion of your own software is fine, especially if it is under open-source license or otherwise freely available with few restrictions.

Answer 3

I would add Google books to the suggested sites to link to, especially when it contains a preview of the book. Google books also provide BibTeX entries, albeit referring to Google books.

In the same way, a link to an Amazon site can be helpful, especially when it has a book preview, providing the links do not give Amazon partner codes (unless there is a TEX-SE or TUG partnership that could benefit from our book purchases, perhaps?).

Finally, if there is a web site of the author or publisher that provides extracts, synopsis, errata or supporting materials then that may be worth a link.