Brihat Parashara Hora Shastra
स्वर्क्षादिकेन्द्रपतयस्तुर्यांशेशाः क्रियादिषु। सनकश्च सनन्दश्च कुमारश्च सनातनः॥ ९॥
Chaturthāńś. The Lords of the 4 Kendras from a Rāśi are the rulers of respective Chaturthāńś of a Rāśi, commencing from Mesh. Each Chaturthāńś is one fourth of a Rāśi. The deities, respectively, are Sanak, Sanand, Kumar and Sanatan.
english translation
svarkSAdikendrapatayasturyAMzezAH kriyAdiSu। sanakazca sanandazca kumArazca sanAtanaH॥ 9॥
hk transliteration by Sanscript