Tat tvam asi; Thou art That of the Chandogya Upanishad, Sama Veda. Ayam atma brahma; This Self is Brahman of Mandukya Upanishad, Atharva Veda. Prajnanam brahma; Brahman is pure consciousness of ...
The Upanishads that you can study in the website are Aitareya, Ishavasya, Karika, Katha, Kena, Mundaka, Mandukya, Prasna, Brihadaranyaka, Shvetashvatara and Taittiriya. Link - You can read and study ...