Natyashastra
परिवर्ताश्च चत्वारः पाणयस्त्रय एव च । जात्या चैव हि विश्लोका तां च तालेन योजयेत् ॥ ६१॥
"The transitions are four, and the hands are three. The types are also differentiated by their verses, and they should be arranged with the rhythm."
english translation
parivartAzca catvAraH pANayastraya eva ca । jAtyA caiva hi vizlokA tAM ca tAlena yojayet ॥ 61॥
hk transliteration by Sanscript