Hartman, Philip; Nirenberg, Louis On spherical image maps whose Jacobians do not change sign. (English) Zbl 0094.16303 Am. J. Math. 81, 901-920 (1959). Page: −5 −4 −3 −2 −1 ±0 +1 +2 +3 +4 +5 Show Scanned Page Cited in 3 ReviewsCited in 124 Documents MathOverflow Questions: Smoothness of ruled surface (asymptotic) parameterisations Keywords:differential geometric Euclidean spaces PDFBibTeX XMLCite \textit{P. Hartman} and \textit{L. Nirenberg}, Am. J. Math. 81, 901--920 (1959; Zbl 0094.16303) Full Text: DOI