kaTha upanishad IV. 1

[Mani Varadarajan]

Vidya,

The "kaThavalli" is not necessarily the kaTha upanishad we
with which we are all familiar.  Vedanta Desika (13th century)
mentions the kaThavalli or kaTha Sruti frequently, but from
the context it is clear that he isn't referring to the kaTha
upanishad [see SrImad rahasya traya sAra, dvayAdhikAram, for
example.]

Mani