[Advaita-l] Information about Shanti Mantras

[Sudhakar Kabra]

Dear learned members,
We chant shanti mantras before and after the Upanishad recitation.These Mantras are different for different Upanishads but some are common to various upanishads.
I need some clarifications for Shanti Mantras.
1. What qualifies for shanti mantra out of various mantras in vedas/ upanishads?Is there any criteria to fulfill to be a shanti mantra?
2. There is a rishi and a devata for each mantra. Where can I find a reference of these rishis and devatas for the shanti mantras?
Thanks and regards,Sudhakar kabra