Brihat Parashara Hora Shastra
त्रिसप्तभे तु भौमस्य षष्टिरत्र लवोनिता । सार्धांशास्तिथिसंयुक्ता द्विभे रूपं सदाऽङ्गभे ॥ ११॥
Special consideration for Mangal‟s Drishtis. Deduct the longitude of Mangal from that of the Grah, that receives the Drishti. If the sum is 3 Rāśis & c, or 7 Rāśis & c, the degrees etc. be reduced from 60. If it is above 2 Rāśis, the degrees etc. be increased by half of it and superadd 15. If the sum is 6 Rāśis, one Rup is the value.
english translation
trisaptabhe tu bhaumasya SaSTiratra lavonitA । sArdhAMzAstithisaMyuktA dvibhe rUpaM sadA'Ggabhe ॥ 11॥
hk transliteration by Sanscript