Brihat Parashara Hora Shastra
लग्नहोराविलग्नाभ्यां स्फुटमायुः प्रकीर्तितम् । आदौ लग्नाष्टमेशाभ्यां योगमेकं विचिन्तयेत् ॥ ३४॥
This is based on the positions of Lagn‟s Lord, Randhr‟s Lord, Śani, Candr, natal Lagn and Hora Lagn.
english translation
lagnahorAvilagnAbhyAM sphuTamAyuH prakIrtitam । Adau lagnASTamezAbhyAM yogamekaM vicintayet ॥ 34॥
hk transliteration by Sanscript