https://catalog.hathitrust.org/Record/000649245?type%5B%5D=all&lookfor%5B%5D=Pre-S%CC%81am%CC%87kara%20Advaita%20philosophy&ft=

https://babel.hathitrust.org/cgi/pt?id=mdp.39015014166923

Pre-Śaṁkara Advaita philosophy by Sangam Lal Pandey