Y. V. Bogdanskii, “Boundary Trace Operator in a Domain of Hilbert Space and the Characteristic Property of its Kernel”, Ukr. Mat. Zhurn., vol. 67, no. 11, pp. 1450–1460, Nov. 2015, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/2081