1. Seneta, E., Regularly Varying Functions, Berlin: Springer-Verlag, 1976. Translated under the title Pravil’no menyayushchiesya funktsii, Moscow: Nauka, 1985.
2. Adamovic, D.D., Sur quelques propertietes des fonctions a croissance lente de Karamata. I, II, Mat. Vesnik (Beograd), 1966, vol. 3, pp. 123–136, 161–172.
3. Kiguradze, I.T. and Chanturiya, T.A., Asimptoticheskie svoistva reshenii neavtonomnykh obyknovennykh differentsial’nykh uravnenii (Asymptotic Properties of Solutions of Nonautonomous Ordinary Differential Equations), Moscow, 1990.
4. Kostin, A.V., The Asymptotic Behavior of the Extendable Solutions of Equations of Emden-Fowler Type, Dokl. Akad. Nauk SSSR, 1971, vol. 200, no. 1, pp. 28–31.
5. Kostin, A.V. and Evtukhov, V.M., Asymptotic Behavior of the Solutions of a Certain Nonlinear Differential Equation, Dokl. Akad. Nauk SSSR, 1976, vol. 231, no. 5, pp. 1059–1062.