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The concept here is identifying an early astronomer’s specific description of the Moon’s geography. Kepler’s Somnium contains a notable passage in which the Moon is described as divided into two hemispheres, called Subvolva and Privolva, a terminology used in that dream‑vision discussion of lunar geography. This exact naming comes from Kepler’s work, making it the best source among the options for this detail.

The other works focus on different topics: Copernicus’s De revolutionibus argues for the heliocentric model; Kepler’s Astronomia Nova explores planetary motion and the orbits of Mars; Galileo’s Sidereus Nuncius reports telescopic discoveries like Jupiter’s moons and lunar features, but not the Subvolva/Privolva terminology.