Shiva Purana
द्वितीयावरणे पूज्याः पूर्वादिपरितः क्रमात् ॥ सनत्कुमारः सनकः सनंदश्च सनातनः ॥ ४१ ॥
Sanat, Sanaka, Sananda and Sanātana shall be worshipped in the second Āvaraṇa all round beginning with the east.
english translation
dvitIyAvaraNe pUjyAH pUrvAdiparitaH kramAt ॥ sanatkumAraH sanakaH sanaMdazca sanAtanaH ॥ 41 ॥
hk transliteration by Sanscript