Chapter 3: Appearance and Reality in Ancient India
The Ṛg Veda can be found at http://www.sacred-texts.com/hin/rigveda/index.htm
The Internet Encyclopedia of Philosophy contains an article on the Upaniṣads and Vedas, and a collection of major Upaniṣads can be found at: https://archive.org/details/thirteenprincipa028442mbp/page/n8
Students wishing to understand the Buddha’s philosophy would do well to begin with the articles on the Buddha in the Internet Encyclopedia of Philosophy and the Stanford Encyclopedia of Philosophy.
Students who want to read the Buddha’s teachings for themselves can find translations of the Sutta Pitika, which includes sutras and discourses from the Buddha and his disciples, at https://www.accesstoinsight.org/tipitaka/sutta.html
Various translations of the Milinda Panha (Questions of Milinda) can be found online, including a classic translation by T. W. Rhys Davids as well as more recent translations.
The Nyaya Sutras can be found at https://archive.org/details/NyayaSutra/page/n1
The History of Philosophy in India podcast by Peter Adamson and Jonardon Ganeri explores many of the themes from this chapter and more.