Kupin, S., and L. Golinskii. “On Complex Perturbations of Infinite Band Schrödinger Operators”. Methods of Functional Analysis and Topology 21, no. 3 (September 25, 2015): 237–245. Accessed February 4, 2026. https://zen.imath.kiev.ua/index.php/mfat/article/view/614.