1. A. I. Egorov, Riccati Equations (Fizmatlit, Moscow, 2001) [in Russian].
2. P. Hartman, Ordinary Differential Equations (Wiley, New York, 1964; Mir, Moscow, 1970).
3. R. A. Stafford and J. W. Heidel, “A New Comparison Theorem for Scalar Riccati Equations,” Bull. Amer. Math. Soc. 80(4), 754–757 (1974).
4. I. M. Sobol’, “On Riccati Equations and the Reduction to Them of Linear Equations of the Second Order,” Sov. Phys. Dokl. 65(3), 275–278 (1949).
5. I. M. Sobol’, “Investigation with the Aid of Polar Coordinates of the Asymptotic Behavior of Solutions of a Linear Differential Equation of the Second Order,” Matem. Sborn. 28(3), 707–714 (1951).