Historical Anando and Sariputto

As the English Wikipedia article on the Mahjjima Nikaya is surprisingly empty, I wonder if there has ever been any historical-critical research on Anando and Sariputto:

  • Who where they and were they in agreement with each other about the teachings of the Buddha?
  • Could they have added or distracted from the Buddha’s original teachings?
  • Could they have overstated their positions in the original Sangha?
  • Many religious and philosophical schools in antiquity had an exoterical as well an esoterical teaching. How do we know for sure that what we have in the Nikayas is the esoterical?
  • Could Brahman teachings that the Buddha was not himself in support of have made their way into the Nikayas?

Thanks, Thomas