Bantsur, N. R., & Trofimchuk, E. P. (1998). On the existence and stability of periodic and almost periodic solutions of quasilinear equations with maxima.
Ukrains’kyi Matematychnyi Zhurnal,
50(6), 747–754.
https://umj.imath.kiev.ua/index.php/umj/article/view/4884