Phaladeepika
मान्दिस्थराशिपतिसङ्गतसुत्रिकोणं तस्यांशराशिपतिसंयुतमंशकोणम् । लग्नं वदन्ति गुलिकांशकराशिकोणं तद्वद्विधौ बलयुते शशिनैव विद्यात् ॥ १६॥
Note the Rasi occupied by Mandi at a birth and note also where the lord of that Rasi is posited. The Lagna at birth will be a position triangular to that of the aforesaid lord or one triangular to the Navamsa occupied by the owner of the sign representing the Navamsa occupied by Mandi. It may be triangular to the Navamsa Rasi occupied by Gulika. When the Moon is strong, the Lagna should be deduced similarly through the Moon alone instead of through Mandi.
english translation
mAndistharAzipatisaGgatasutrikoNaM tasyAMzarAzipatisaMyutamaMzakoNam । lagnaM vadanti gulikAMzakarAzikoNaM tadvadvidhau balayute zazinaiva vidyAt ॥ 16॥
hk transliteration by Sanscript