buddavacana

Dear Dhamma Friends,

I was reading about what is called the "Four great appeals to authority" (caturmahapadesa), which defines and allows Buddhavacana to be teachings spoken by:

*The Buddha himself
*A Sangha of Elders
*A group of specialists in either the suttas, vinaya or matrkas
* A single specialist in one of these three areas

The author says that these "Four Appeals" appear in the Digha Nikaya and Anuttara Nikaya as part of the Buddha's final instructions.

Is this information correct? If so, in which texts this statements by Buddha appear?

Thank you very much for any clarification,
tenphel