Two-to-one transformations on 2-manifolds
Venable Martin, J. H. Roberts · Transactions of the American Mathematical Society · 1941
This paper will be referred to hereafter as Transformations.(3) See abstracts in the Bulletin of the American Mathematical Society, vol.45 (1939), p. 835, and vol.46 (1940), pp.42, 43.(4) This follows readily from the compactness of M.However, the corresponding statement in Transformations does not follow from the continuity of T, and must be taken as an extra hypothesis in those theorems of that paper where M was not assumed to be compact.This does not affect the main result of that paper. 1