On oscillation and boundedness of solutions of nonlinear differential equations Gerasimos Ladas — 1969 Δελτίο της Ελληνικής Μαθηματικής Εταιρίας
Necessary and sufficient conditions for oscillation of delay equations with constant coefficients Myron K. Grammatikopoulos; Gerasimos Ladas; Yiannis G. Sficas — 1987 Czechoslovak Mathematical Journal