1. Helgason, S.: Groups and Geometric Analysis, Integral Geometry, Invariant Differential Operators and Spherical Functions, Academic Press, New York, 1984
2. Burns, J. M.: Conjugate loci of totally geodesic submanifolds of symmetric spaces. Trans. Amer. Math. Soc., 337, 411–425 (1993)
3. Koike, N.: Tubs of nonconstant radius in symmetric spaces. Kyushy J. Math., 56, 267–291 (2002)
4. Bishop, R. L., Crittenden, R. H.: Geometry of manifolds, Academic Press, New York, 1964
5. Helgason, S.: Differential Geometry, Lie Groups, and Symmetric spaces, Academic Press, New York, 1978