Valmiki Ramayana Yuddha Kanda Sarga 4 Shloka 15

गिरिसङ्काशः one in the form of a mountain,गजश्च Gaja, महाबलः mighty strong, गवयश्च Gavaya, गवाक्षश्च and Gavaksha, दृप्तः proud, ऋषभः bulls,गवाम् इव like the cows,अग्रतः that go in front, यातु would go

"Gaja who is like a mountain in form, Gavaya, the mighty strong and Gavaksha would go like proud bulls that lead the cows".