Real analytic projective planes with large automorphism groups. Immervoll, Stefan — 2003 Advances in Geometry
Homogeneous spaces and isoparametric hypersurfaces. Immervoll, Stefan — 2008 Beiträge zur Algebra und Geometrie
A characterization of isoparametric hypersurfaces of Clifford type. Immervoll, Stefan — 2004 Beiträge zur Algebra und Geometrie