[1] Coddington E. A., Levinson N.: Theory of Ordinary Differential Equations. McGraw-Hill, New York 1955. MR 0069338 | Zbl 0064.33002

[2] Gregor J.: Dynamical systems with regular right-hand side. (in Czech). Pokroky MF A, III, No 2 (1958), 153-160.

[3] Hájek O.: Conformal mapping of neighbourhoods of singular points in meromorphic dynamical systems. presented at the 1955 conference of the Prague Institute of Technology (unpublished).