1. Sansone, G.: Equazioni differenziali nel campo reale. Bologna: N. Zanichelli, 1948
2. Avakumović, V. G.: On differential equations of the Thomas-Fermi type (Serbo-Croatian). Glas Srpske Akad. Nauka191, 163–187 (1948)
3. Wong, P. K.: Existence and asymptotic behavior of proper solutions of a class of second-order nonlinear differential equations. Pacific. J. Math.13, 737–760 (1963)
4. Avakumović, V. G.: Sur une extension de la condition de convergence des théoremes inverses de sommabilité. C.r. Acad. Sci., Paris200, 1515–1517 (1935)
5. Karamata, J.: Remark on the preceding paper by V. G. Avakumović, with the study of a class of functions occuring in the inverse theorems of the summability theory (Serbo-Croatian). Rad Jugoslav. Akad. Znanost. Umjetnost.254, 187–200 (1936)