Brihat Parashara Hora Shastra
विशोध्यार्णवतो द्वाभ्यां लब्धं त्रिंशद्युतं च दृक् । द्व्यधिके तु विना राशिं भागास्तिथियुतास्तथा ॥ ८॥
If the difference is in excess of 3 Rāśis, deduct it from 4 Rāśis and (increase 30 by) halve the product to get the Drishti value. If the difference is above 2 Rāśis, ignore the Rāśis and add 15 to the degrees etc. to get the Drishti value. If it is in excess of one Rāśi, ignore the Rāśis and divide the degrees by 2 to get the Drishti value.
english translation
vizodhyArNavato dvAbhyAM labdhaM triMzadyutaM ca dRk । dvyadhike tu vinA rAziM bhAgAstithiyutAstathA ॥ 8॥
hk transliteration by Sanscript