Natyashastra
मुखं प्रतिमुखं चैव वैहायसकमेव तु । स्थितप्रवृत्ते वज्रं च सन्धिः संहरणं तथा ॥ ४॥
The Mukha, Pratimukha, Vaihāyasaka, Sthita, Pravṛtta, Vajra, Sandhi, and Saṃharaṇa are parts (aṅgas) of the Dhruvā songs.
english translation
mukhaM pratimukhaM caiva vaihAyasakameva tu । sthitapravRtte vajraM ca sandhiH saMharaNaM tathA ॥ 4॥
hk transliteration by Sanscript