1. Uniqueness theorems for surfaces in the large, I;Alexandrov;Vestnik Leningrad Univ. Math.,1956
2. Nonlinear eigenvalue problems having precisely two solutions;Amann;Math. Z.,1976
3. Submanifolds and Holonomy;Berndt,2016
4. Generalized Heisenberg Groups and Damek-Ricci Harmonic Spaces;Berndt,1995
5. Manifolds All of Whose Geodesics Are Closed;Besse,1978