Praudhamanorama p59

p59

"There is no visarga": and this is identical in sukhārtaḥ and so forth as well. And here, in the view that metarules apply at the time of operation, the non-effectiveness on account of being an external operation should also be understood. Nor is there the prohibition "[an operation conditioned by an internal cause is not unaccomplished] with respect to proximity of vowels"; for even though it would apply in the view of Haradatta, namely that [it applies] wherever there is proximity of two vowels either in an internal operation or in an external operation, according to Kaiyaṭa's opinion—that [it applies only] where there is proximity of two vowels in what applies subsequently—the prohibition does not apply. For even if proximity of two vowels exists in vṛddhi, which is external because it is dependent on many things, it is absent in what applies subsequently. "By a preverb": because it has been stated that the technical names gati and upasarga belong to the words beginning with pra only with respect to that action with which they are connected—this is the purport.
[Pā. sū. 6.1.92] "Optionally according to Āpiśali when a nominal ending follows."