Brihat Parashara Hora Shastra
त्रिसप्तभे तु जीवस्य भागार्धं शरवेदयुक् । द्विगुणैस्तु लवैश्चोनाः खरसाश्चतुरष्टभे ॥ १२॥
Special consideration for Guru‟s Drishtis. Deduct the longitude of Guru from that of the Grah, that receives the Drishti from Guru. If the resultant sum is 3 Rāśis & c, or 7 Rāśis & c, halve the degrees etc. and increase it by 15. It the sum is 4 Rāśis & c, or 8 Rāśis & c, the degrees etc. be subtracted from 60.
english translation
trisaptabhe tu jIvasya bhAgArdhaM zaravedayuk । dviguNaistu lavaizconAH kharasAzcaturaSTabhe ॥ 12॥
hk transliteration by Sanscript