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 == Adviatia doesn't belong to the lead/Introduction == 

 This is an article focused on the Upanishads and while the Upanishads, the Brahmasutra and the Gita may have influenced Vedantic schools such as Advaita, there's no need to over emphasize Advaita in the article. Particularly, the lead/introduction section should have information that's only directly relevant to the Upanishads - no need to have Advaita here. I have restored the lead as follows: 

 The Upanishads (Devanagari: उपनिषद्, IAST: Upaniṣad, also spelled ""Upaniṣad"") are a collection of more than 200 philosophical texts of the Hindu religion. The first dozen or so texts are the most important, and they are variously referred to as the Principal Upanishads, mukhya or main Upanishads, and the old Upanishads. The oldest of the mukhya Upanishads were composed during the pre-Buddhist era of India, and have been passed down the generations in oral tradition. The mukhya Upanishads hold the stature of revealed texts or shruti amongst Hindu scriptures. Along with the Bhagavad Gita, and the Brahmasutra,[1] the mukhya Upanishads provide a foundation for several later schools of Indian philosophy. 

 The Upanishads do not belong to any particular period of Sanskrit literature. The oldest, such as the Brihadaranyaka and Chandogya Upanishads, date to the late Brahmana period around the middle of the first millennium BCE, while the new Upanishads were composed in the medieval and early modern period; discoveries of newer Upanishads were being reported as late as 1926.[2] The newest Upanishads are known to be imitations of the mukhya Upanishads. The Upanishads are collectively considered amongst the 100 Most Influential Books Ever Written by the British poet Martin Seymour-Smith. 

 One new Upanishad, the Muktika Upanishad, predates 1656[3] and contains a list of 108 canonical Upanishads[4], listing itself as the final one. Dara Shikoh, son of the Mughal emperor Shah Jahan, translated fifty Upanishads into Persian in 1657. The first written English translation came in 1804 from Max Müller; he was aware of 170 Upanishads. Sadhale's catalog from 1985 is called the Upaniṣad-vākya-mahā-kośa and it lists 223 Upanishads.[5] The Upanishads are mostly the concluding part of the Brahmanas and the transition from the latter to the former is identified as the Aranyakas.[6] 

 An additional line can be added if we can reach consensus: 

 On the one hand, the ideas of the Upanishads are said to have made the greatest contribution to human thought and on the other, Huxley states that the voluminous work can be reduced to only a few words, i.e., the equation of Brahman with the Atman. 

 Thanks.   "