Answer: These are religious books of Hindus
Notes: The Upanishads are a collection of texts of religious and philosophical nature. These were written in India probably between 800 BCE and 500 BCE.The teachings of the Upanishads revolve around four primary spiritual themes. The first and most important is the realization that the ultimate, formless, and inconceivable Brahman is the same as Atman, as our internal soul. The Brihadaranyaka Upanishad is one of the Principal Upanishads and one of the oldest Upanishadic scriptures of Hinduism.
