I usually have the problem that can't find many books on topics I am interested in. For example: If I want books about Mongolia, I can search at an online books store, and I'll find some books, but if had know specific titles, or certain historians, I would have found more, or more specialized. Not only the one that are available to that certain bookstore. Does anyone have experience with this problem? Or there any websites where you can search for a topic in general, and it shows you all the books that have been wirten about said topic?

Thank you for your help, greetings from Germany.