Shiva Purana
कौरवाणां स आचर्य्यं आसीत्स्वबलतो द्विज ॥ महारथिषु विख्यातः षट्सु कौरवमध्यतः ॥ ५॥
O brahmin, thanks to his strength, he was the instructor of the Kauravas. He was the most well known among the six Mahārathas among the Kauravas.
english translation
kauravANAM sa AcaryyaM AsItsvabalato dvija ॥ mahArathiSu vikhyAtaH SaTsu kauravamadhyataH ॥ 5॥
hk transliteration by Sanscript