Brihat Parashara Hora Shastra
ज्ञेयाश्चरस्थिरद्वन्द्वाः क्रमतो बलशालिनः । राशिसत्त्वसमानत्वे बहुवर्षो बली भवेद् ॥ १६३॥
If there is equality in the strength of the Rāśis, then to determine the number of years of Dasha counting should be done up to the Rāśi with bigger number.
english translation
jJeyAzcarasthiradvandvAH kramato balazAlinaH । rAzisattvasamAnatve bahuvarSo balI bhaved ॥ 163॥
hk transliteration by Sanscript