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On Certain Asymptotic Properties of the Solutions of the Equation $\dot{z}=f(t,z)$ with a Complex-Valued Function f. Czechoslovak Mathematical Journal, to appear. 
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Geometrical Approach to the Study of the Riccati Differential Equation with Complex-Valued Coefficients. Journal of Differential Equations 25 (1977), 108-114. 
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MR 0268452