Natyashastra
एतेषां चापि वक्ष्यामि विधिं प्रकृतिसम्भवम् ज्येष्ठानां वृत्तसंयुक्तं कुर्यादादौ तथैव च । विवधं चैव मध्यानां नीचानामेककं तथा ॥ १८॥
And now I shall explain the method of these, arising from their natural order. For the superior ones, one should first employ the Vṛtta combined with measures. For the middling ones, the Vivadha should be used, and for the inferior ones, the Ekaka.
english translation
eteSAM cApi vakSyAmi vidhiM prakRtisambhavam jyeSThAnAM vRttasaMyuktaM kuryAdAdau tathaiva ca । vivadhaM caiva madhyAnAM nIcAnAmekakaM tathA ॥ 18॥
hk transliteration by Sanscript