Huang, Sen-Zhong, Hermann Render, and Manfred P. H. Wolff. “On the Convergence of Sequences of Operators and the Convergence of the Sequence of Their Spectra”. Mathematica Scandinavica 85, no. 1 (September 1, 1999): 71–78. Accessed July 24, 2026. https://journals.msp.org/mscand/article/view/943.