Bel’skii, D. V., & Pelyukh, G. P. (2005). On the behavior of solutions of linear functional differential equations with constant coefficients and linearly transformed argument in neighborhoods of singular points.
Ukrains’kyi Matematychnyi Zhurnal,
57(12), 1668–1676.
https://umj.imath.kiev.ua/index.php/umj/article/view/3717