Ostrovskii, V. L., and Yu. S. Samoilenko. 2006. “On Spectral Theorems for Families of Linearly Connected Self-Adjoint Operators With Given Spectra Associated With Extended Dynkin Graphs”. Ukrains’kyi Matematychnyi Zhurnal 58 (11): 1556–1570. https://umj.imath.kiev.ua/index.php/umj/article/view/3554.