Brihat Parashara Hora Shastra
यथा तुर्यस्थिते नाथे तुर्यमेव पदं भवेत् । सप्तमे च स्थिते नाथे विज्ञेयं दशमं पदम् ॥ ५॥
Similarly, when the 7th becomes the Pad of a Bhava, the 4th from the original Bhava in question be treated, as its Pad. If the ruler of a Bhava be in the 4th from the Bhava, then the very Bhava occupied be noted, as the Pad.
english translation
yathA turyasthite nAthe turyameva padaM bhavet । saptame ca sthite nAthe vijJeyaM dazamaM padam ॥ 5॥
hk transliteration by Sanscript