Verezhak, A. P., et al. “A Problem for One Class of Pseudodifferential Evolutionary Equations Multipoint in the Time Variable”. Ukrains’kyi Matematychnyi Zhurnal, vol. 70, no. 3, Mar. 2018, pp. 337-55, https://umj.imath.kiev.ua/index.php/umj/article/view/1560.