A.Sh. Shaldanbayev, S.M. Shalenova, M.B. Ivanova, и A.A. Shaldanbayeva. «ON SPECTRAL PROPERTIES OF A BOUNDARY VALUE PROBLEM OF THE FIRST ORDER EQUATION WITH DEVIATING ARGUMENT». Известия НАН РК. Серия физико-математическая, вып. 5, октябрь 2019 г., сс. 19-39., http://189185.vm7pq.group/physics-mathematics/article/view/1656.