. "The Principal Upanishads"@en . "81-7223-124-5" . . "958"^^ . . . "The Principal Upanishads is a 1953 book written Sarvepalli Radhakrishnan (1888\u20131975), then Vice President of India (and later President of India), about the main Upanishads, which carry central teachings of the Vedanta."@en . . .