Surya Siddhanta
शसाङ्कार्कयुतेर् लिप्ता भभोगेन विभाजिताः। लब्धम् सप्तदशान्तो +अन्यो व्यतीपातस् तृतीयकः॥
If the sum of the longitudes of the sun and moon, in minutes, on being divided by the portion (bhoga) of an asterism (bha), yields a quotient between sixteen and seventeen, there is another, a third, vyatipdta. (If the sum of longitude of sun and moon in kaläs is divided by 27, and if this quotient is in the region of 17, then we have a third aspect called vyatégata.)
english translation