Wikipedia is the Biggest Multilingual Free-Content Encyclopedia on the Internet. You can explore it concerning to Kriya Yoga.
Links about the Science of Kriya Yoga (explanation, personal experiencies, Kriya Yoga Library, documents, Books, etc.)
Links of Webstores which comercialize Kriya Yoga books in internet.
You can buy and search Kriya Yoga english, spanish and other language books, referred in this website, in the following links:
If you want to buy in Portugal the books referred in this website, you can do it. For this propose contact the following bookstores.