Brihat Parashara Hora Shastra
द्वादशांशस्य गणना तत्तत्क्षेत्राद्विनिर्दिशेत्। तेषामघीशाः क्रमशो गणेशाऽश्वियमाहयाः॥ १५॥
Dvadashāńś. The reckoning of the Dvadashāńś (one twelfth of a Rāśi, or 2½ degrees each) commences from the same Rāśi. In each Rāśi the presidentship repeats thrice in the order of Ganesh, Ashvini Kumar, Yama and Sarpa for the 12 Dvadashāńśas.
english translation
dvAdazAMzasya gaNanA tattatkSetrAdvinirdizet। teSAmaghIzAH kramazo gaNezA'zviyamAhayAH॥ 15॥
hk transliteration by Sanscript