Natyashastra
ध्रुवास्तु पञ्च विज्ञेया नानावृत्तसमुद्भवाः । यथास्थानरसोपेता ह्युत्तमाधममध्यमाः ॥ २५॥
The Dhruvās are five in number and arise from various metres; according to their placement and the sentiments they convey, they are suitable for superior, inferior, and middling characters.
english translation
dhruvAstu paJca vijJeyA nAnAvRttasamudbhavAH । yathAsthAnarasopetA hyuttamAdhamamadhyamAH ॥ 25॥
hk transliteration by Sanscript