Natyashastra
ध्रुवास्तु पञ्च विज्ञेया नानासंस्थानसंश्रयाः । एतासां सम्प्रवक्ष्यामि सप्तरूपाङ्गकारणम् ॥ ९॥
The Dhruvās are to be known as five in number, based on their different conditions of use; I shall now explain the reason for their sevenfold structure and limbs.
english translation
dhruvAstu paJca vijJeyA nAnAsaMsthAnasaMzrayAH । etAsAM sampravakSyAmi saptarUpAGgakAraNam ॥ 9॥
hk transliteration by Sanscript