Oscillations of all solutions of functional differential inequalities Jarosław Werbowski — 1986 Czechoslovak Mathematical Journal
Note on the asymptotic behavior of the solutions of differential equations with deviating arguments Jarosław Werbowski — 1978 Mathematica Slovaca
Oscillation of linear functional equations of higher order W. Nowakowska; Jarosław Werbowski — 1995 Archivum Mathematicum The paper contains sufficient conditions under which all solutions of linear functional equations of the higher order are oscillatory.
Conditions for the oscillation of solutions of iterative equations. Nowakowska, Wiesława; Werbowski, Jarosław — 2004 Abstract and Applied Analysis