Q: How can I search for books in a particular language?

I have looked on the store, and am unaware of a way to search for books in any particular language. When I click on the option to search by language, many languages do come up, but not all. I would love to search through the Esperanto books, but this is not listed as a language which one can search by. If anybody knows how I can do this, then that would be very helpful. Thank you!