问题

[命题] 紧致黎曼曲面之间的每个非常值全纯映射都是有限层(分歧)覆盖映射.

Every non-constant holomorphic mapping between compact Riemann surfaces is a finite-sheeted (ramified) covering map.

见 [1] pp.15 Example.

[1]  Hershel M. Farkas, Irwin Kra,  Riemann Surfaces, 2nd edition.  GTM 71.