@article{700177,
     title = {On properties of oscillatory solutions of non-linear differential equations of the n-th order},
     booktitle = {Equadiff 6},
     series = {GDML\_Books},
     publisher = {J. E. Purkyn\v e University, Department of Mathematics},
     address = {Brno},
     year = {1986},
     pages = {[109]-113},
     mrnumber = {MR0877111},
     zbl = {0603.34026},
     url = {http://dml.mathdoc.fr/item/700177}
}

Bartušek, Miroslav. On properties of oscillatory solutions of non-linear differential equations of the n-th order, dans Equadiff 6, GDML_Books,  (1986), pp. [109]-113. http://gdmltest.u-ga.fr/item/700177/