Is "Young Man on a Riverbank (recto); Study of a Wagnerian Scene (verso)" in the public domain?

Yes, Young Man on a Riverbank (recto); Study of a Wagnerian Scene (verso) is in the public domain and available for free download under CC0 license.

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Young Man on a Riverbank (recto); Study of a Wagnerian Scene (verso)

Umberto Boccioni, 1902