BrascheJ. F., KoshmanenkoV. D. and NeidhardtH. (1994) “New aspects of Krein’s extension theory”, Ukrains’kyi Matematychnyi Zhurnal, 46(1-2), pp. 37–54. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/5768 (Accessed: 1September2024).