William Dwight Whitney,
Sanskrit Grammar
(This republication 1950, original 1889)
“ The nasals are more freely combinable: a nasal may either precede or follow a mute of either kind, or the sonant spirant h; it may also follow a surd aspirant (sibilant) ; no nasal, however, ever precedes a sibilant in the interior of a word (it is changed instead to anusvāra) ; and in external combination their concurrence is usually avoided by insertion of a surd mute. d. A semivowel has still less sonantizing influence; and a vowel least of all: both are freely preceded and followed by sounds of every other class, in the interior of a word. ”
