Natyashastra
श्रोतोगता च गोपुच्छासमा चात्र विधाय च । लयप्रवृत्तवर्णानामक्षराणामथापि वा ॥ ३३३॥
The three kinds—Śrotogatā (flowing forward), Gopucchā (tapering like a cow’s tail), and Samā (even)—are to be applied here, referring to the arrangement of syllables that follow the course of rhythm and tempo.
english translation
zrotogatA ca gopucchAsamA cAtra vidhAya ca । layapravRttavarNAnAmakSarANAmathApi vA ॥ 333॥
hk transliteration by Sanscript