Brihat Parashara Hora Shastra
लग्नसप्तमयोर्मध्ये यो राशिर्बलवान् भवेत् । ततः केन्द्रादिसंस्थानां राशीनाञ्च बलक्रमात् ॥ १७५॥
In this system there are Dashas of Fixed Rāśis in the Kendr etc. from Lagn, or from Yuvati, whichever is stronger. If Lagn, or Yuvati with strength is placed in an odd Rāśi, the Kendr etc. are counted in the onward order. If it be in an even Rāśi, the counting will be in the backward, or reverse order.
english translation
lagnasaptamayormadhye yo rAzirbalavAn bhavet । tataH kendrAdisaMsthAnAM rAzInAJca balakramAt ॥ 175॥
hk transliteration by Sanscript