(266) A. Domoshnitsky; Wronskian of fundamental system of delay differential equations, Funct. Differ. Equ. 9, No.3-4, 353-376 (2002).

(267) A. Domoshnitsky, unboundedness of solutions and instability of differential equations of the second order with delayed argument, Differ. Integral Equ. 14, No.5, 559-576 (2001).

(268) M. Feèkan, Existence of almost-periodic solutions to jumping discontinuous systems, Acta Math. Hung. 86, No.4, 291-303 (2000).

(269) John R. Graef - Jaános Karsai, Behaviour of solutions of impulsively perturbed non-halflinear oscillator equations, J. Math. Anal. Appl. 244, No.1, 77-96 (2000).

(270) Akhmet, M. u.; Büyükadal; C. Differential equations with state-dependent piecewise constant argument. Nonlinear Anal. 72 (2010), no. 11, 4200--4210.