Natyashastra
यतिच्छन्दोविधानेन गुरुलघ्वक्षरान्वितः । कार्यो मात्राप्रमाणेन ध्रुवापादोऽवसानिकः ॥ २२॥
The foot of the concluding Dhruvā should be composed of long and short syllables according to the rules of Yati, metre, and measurement in mātrās.
english translation
yaticchandovidhAnena gurulaghvakSarAnvitaH । kAryo mAtrApramANena dhruvApAdo'vasAnikaH ॥ 22॥
hk transliteration by Sanscript