[1] Kаlаs J.: Asymptotic behaviour of the solutions of the equation dz/dt =f(t, z) with acomplex-valued function f. Proceedings of tһe Internаtionаl Colloquium on Quаlitаtive Theory of Differentiаl Equаtions, August 1979, Szeged - Hungаry, Seriа Colloquiа Mаthemаticа Societаtis János Bolyаi & North-Hollаnd Publishing Compаny, pp. 431-462.

[2] Kаlаs J.: On the asymptotic behaviour of the equation dz/dt =f(t,z) with a complex-valued function f. Arch. Mаth. (Brno), 17 (1981), 11-22. MR 0672484

[3] Kаlаs J.: On certain asymptotic properties of the solutions of the equation ż = f(t, z) with a complex-valued function f. Czech. Mаth. Journаl, to аppeаr.

[4] Kаlаs J.: Asymptotic properties of the solutions of the equation ż = f(t, z) with a complex-valued function f. Arch. Mаth. (Bmo), 17 (1981) 11З-124.

[5] Ráb M.: The Riccati differential equation with complex-valued coefficients. Czech. Mаth. Journаl 20 (1970), 491-503. MR 0268452

[6] Ráb M.: Geometrical approach to the study of the Riccati differential equation with complex-valued coefficients. J. Differentiаl Equаtions 25 (1977), 108-114. MR 0492454

[7] Ráb M.: Asymptotic behaviour of the equation x" + p(t)x' + q(t)x = 0 with complex-valued coefficients. Arch. Mаth. (Bгno) 11 (1975), 193-204. MR 0404776