Nrsimha Tapania Upanisada
These Upanishad belong to Atharva veda.. Desikan refers to this upanishdas in his works as well. Adiyen dont think there ahs been any commentry on these upanishads.
However Putthur Sri Krishna Swamy Iyengar has dealt with these upanishads in a more extensive form but short of being a commentry in his works viz :- Visishtadwaitha Vijayam and Vishnu Chith Vijayam.
