Daniel 8:6

And he came to the ram that had two horns, which I had seen standing before the river, and ran unto him in the fury of his power.

Cross-reference

Daniel 8:3 introduces the ram (Persia) that the goat attacks in 8:6 — directly linking the two symbols in the same vision.

Daniel 8:23 describes a later little horn arising after the goat's horns — a future stage in the same prophetic timeline.