AdamyanV. M., ArovD. Z., BerezanskyYu. M., GorbachukV. I., GorbachukM. L., MikhailetsV. A., and SamoilenkoA. M. 2007. “Mark Grigorievich Krein (to the Centenary of His Birth)”. Ukrains’kyi Matematychnyi Zhurnal 59 (5), 579-87. https://umj.imath.kiev.ua/index.php/umj/article/view/3333.