Brihat Parashara Hora Shastra
त्रिभागं वसुकोष्ठेषु विन्यस्य तत्फलं वदेत् । एवं द्वादशभावेषु पाचकानि प्रकल्पयेत् ॥ २०६॥
The remaining 8 apartments may be filled in by one third of the aforesaid years, months etc. In this manner Pachak Dasha in Sandhya Dasha of every Bhava can be worked out and predictions may be made from it.
english translation
tribhAgaM vasukoSTheSu vinyasya tatphalaM vadet । evaM dvAdazabhAveSu pAcakAni prakalpayet ॥ 206॥
hk transliteration by Sanscript