B. Bekbolat, B. Kanguzhin, & N. Tokmagambetov. (2019). TO THE QUESTION OF A MULTIPOINT MIXED BOUNDARY VALUE PROBLEM FOR A WAVE EQUATION. Известия НАН РК. Серия физико-математическая, (4), 76–82. извлечено от http://89.250.84.46/physics-mathematics/article/view/1678