Brihat Jataka
सर्वार्द्धत्रिचरणपञ्चषष्ठभागा: क्षीयन्ते व्ययभवनादसत्सु वामम् ॥ सत्स्वर्द्धं ह्रसति तथैकराशिगानामेकोंऽशं हरति बली तथाह सत्य: ॥ ७-३ ॥
When they are malefics, they are diminished by all, half, third, fourth, fifth, and sixth portions left from the 12th house. When they benefics, they are diminished by half (of the values stated for malefics). Thus, of them (planets) situated in one zodiac sign, the one possessed of power losses one portion. Thus says Satya.
english translation
sarvArddhatricaraNapaJcaSaSThabhAgA: kSIyante vyayabhavanAdasatsu vAmam ॥ satsvarddhaM hrasati tathaikarAzigAnAmekoM'zaM harati balI tathAha satya: ॥ 7-3 ॥
hk transliteration by Sanscript