Zapryanov, Zapryan. “Dispertion Equation of Wave Regime for Film Frainage With Elastic Properties of Interface Boundaries”. Ann. Sofia Univ. Fac. Math. and Inf. 86, no. 2 (December 12, 1994): 169–179. Accessed April 3, 2025. https://ftl5.uni-sofia.bg./index.php/fmi/article/view/511.