# Citable Reference for Picard's Theorem in Banach Space

I was wondering if anyone knew of a legitimate citable reference where Picard's Theorem on the existence of solutions to ODEs in Banach space is proven? For some reason I can only find proofs for the case of $\mathbb{R}^n$ in any of the books I have looked at. I realize that the proof is the same, but I would like to have a reference where I do not have to mention this fact.

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