Sahityarathi Lakshminath Bezbaroa's book on Vaishnavism titled 'তত্ত্ব-কথা' (Tattva-Katha) is now available on Assamese wikisource. I thank all the wikimedians who participated in creating the unicode form and proof-reading of the book. Here is the link to the page: https://as.wikisource.org/wiki/Tattva-Katha