2 citations to https://www.mathnet.ru/rus/im7164

1. Spitkovsky I.M., Weis S., “Signatures of Quantum Phase Transitions From the Boundary of the Numerical Range”, J. Math. Phys., 59:12 (2018), 121901        
2. Weis S., “Maximum-Entropy Inference and Inverse Continuity of the Numerical Range”, Rep. Math. Phys., 77:2 (2016), 251–263