Efendiev, V. V., and V. P. Zheltikov. “Boundary-Layer Averaging for Standard Systems With Lag”. Ukrains’kyi Matematychnyi Zhurnal 46, no. 10 (October 25, 1994): 1362–1368. Accessed December 6, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/5614.