Fegan, Howard D.; Steer, Brian Invariant operators with complex potentials. (English) Zbl 1264.58028 C. R. Math. Acad. Sci., Soc. R. Can. 33, No. 4, 107-115 (2011). MSC: 58J53 Isospectrality 57S25 Groups acting on specific manifolds PDFBibTeX XMLCite \textit{H. D. Fegan} and \textit{B. Steer}, C. R. Math. Acad. Sci., Soc. R. Can. 33, No. 4, 107--115 (2011; Zbl 1264.58028)