Brihat Parashara Hora Shastra
राहोस्तु वृषभं केतोर्वृश्चिकं तुङ्गसंज्ञकम् । मूलत्रिकोणकं ज्ञेयं युग्मं चापं क्रमेण च ॥ ३५॥
The exaltation Rāśi of Rahu is Vrishabh. The exaltation Rāśi of Ketu is Vrischik. The Multrikonas of Rahu and Ketu are Mithun and Dhanu.
english translation
rAhostu vRSabhaM ketorvRzcikaM tuGgasaMjJakam । mUlatrikoNakaM jJeyaM yugmaM cApaM krameNa ca ॥ 35॥
hk transliteration by Sanscript