Gerus, Oleg F. “On the Spectra of a Quaternion Singular Integral Operator and Its Components on Spatial Surfaces”. Bulletin de la Société des Sciences et des Lettres de Łódź 70, no. 1 (August 12, 2021): 153–167. Accessed September 13, 2026. https://journals.ltn.lodz.pl/Bulletin/article/view/1270.