Natyashastra
चतुर्विधं च विज्ञेयमातोद्यं लक्षणान्वितम् । ततं तन्त्रीगतं ज्ञेयमवनद्धं तु पौष्करम् ॥ २८॥
The four kinds to be understood are: the ascending (Udyam) with specific characteristics, the one associated with strings (Tantrigata), the one with a flat tone (Avanaddha), and the one with a full, robust quality (Poushkara).
english translation
caturvidhaM ca vijJeyamAtodyaM lakSaNAnvitam । tataM tantrIgataM jJeyamavanaddhaM tu pauSkaram ॥ 28॥
hk transliteration by Sanscript