Hi, I'm searching for books, articles, or any other kind of infromation sources on business models that companies developing linux distros use, or could use.

I've been looking for these with keywords like linux/freemium/business models/companies and by looking for specific companies directly, but i haven't found much. Is there anyone here, by any chance, who knows of such works, and can reccomend me some? I'm a student of economics and I need some sources for my thesis.