Brihat Parashara Hora Shastra
अस्तगस्तु हरेत्स्वार्ध विना शुक्रशनैश्चरौ । वक्रचारं विना त्र्यांशां शज्ञुराशौ हरेद् ग्रहः ॥ ९॥
Rectifications. Excepting Śukr and Śani, the contributions, made by others, should be halved, if they are eclipsed by Sūrya. One third should be reduced, if the Grah is in its inimical Rāśi. This does not apply to the one in retrogression (see Vakra Charam).
english translation
astagastu haretsvArdha vinA zukrazanaizcarau । vakracAraM vinA tryAMzAM zajJurAzau hared grahaH ॥ 9॥
hk transliteration by Sanscript