Praudhamanorama p21

p21

[On] 'along with the vowel ā': and here, designations such as 'kālasamayavelāsu' (P. 3.3.167) are the clue for coalescence (praśleṣa). Nor should it be said that even so, in forms like 'yiyā3so', retroflexion of the 's' of the suffix 'san' after a prolated 'a' by 'guroranṛtaḥ' (P. 8.2.86) would definitely occur, because of the explanation that in the dvandva compound 'āśca āśca' ('ā and ā'), by homogeneous lengthening, there is coalescence of the prolated vowel as well after the long vowel. [On] 'semivowels and the rest': homogeneous lengthening in the word 'śītala' is the meaning of the word 'and the rest' (ādi).
'aṇudit savarṇasya cāpratyayaḥ' (P. 1.1.69)