The rise of Buddhism and Jainism, su Religion and Ethics—Hinduism: Other religious influences, BBC, 26 luglio 2004. URL consultato il 21 aprile 2007.
books.google.com
[1] Paul Deussen, Philosophy of the Upanishads: "these treatises are not the work of a single genius, but the total philosophical product of an entire epoch which extends [from] approximately 1000 or 800 BC, to c.500 BCE, but which is prolonged in its offshoots far beyond this last limit of time." pag.51
Adams, C. J., Classification of religions: Geographical, Encyclopædia Britannica, 2007. Accessed: 15 July 2010 "Indian religions, including early Buddhism, Hinduism, Jainism, and Sikhism, and sometimes also Theravāda Buddhism and the Hindu- and Buddhist-inspired religions of South and Southeast Asia".
Indiana University "India Studies Program"Archiviato il 1º agosto 2009 in Internet Archive. Passage to India, Module 10. "Upanishads came to be composed already in the ninth and eighth century B.C.E. and continued to be composed well into the first centuries of the Common Era. The Brāhmaṇas and Āraṇyakas are somewhat older, reaching back to the eleventh and even twelfth century BCE."
web.archive.org
Adherents.com, Religions by adherents, su adherents.com. URL consultato il 9 febbraio 2007 (archiviato dall'url originale il 29 dicembre 2011).
Indiana University "India Studies Program"Archiviato il 1º agosto 2009 in Internet Archive. Passage to India, Module 10. "Upanishads came to be composed already in the ninth and eighth century B.C.E. and continued to be composed well into the first centuries of the Common Era. The Brāhmaṇas and Āraṇyakas are somewhat older, reaching back to the eleventh and even twelfth century BCE."