Natyashastra
एकवस्तु ध्रुवा ज्ञेया द्विवस्तु परिगीतिका । त्रिवस्तु मद्र कं ज्ञेयं चतुर्वस्तु चतुष्पदा ॥ ७॥
A song containing one Vastu is called a Dhruvā; one with two Vastus is a Parigītikā; one with three is known as a Madraka; and one with four Vastus is a Catuṣpadā.
english translation
ekavastu dhruvA jJeyA dvivastu parigItikA । trivastu madra kaM jJeyaM caturvastu catuSpadA ॥ 7॥
hk transliteration by Sanscript