Papers and Preprints:

• A metric characterization of spherical and Euclidean buildings. Geometry and Topology, Vol.5 (2001),521-550 (with Ruth Charney)
• On the geometry of subsets of positive reach. Manuscripta Math., Vol.115 (2004), 199-205
• Differentiation in metric spaces. Algebra i Analiz, Vol.16 (2004), 128-161
• Open map theorem in metric spaces. Algebra i Analiz, Vol.17 (2005), 139-159
• Almost convex subsets. Geom. Dedicata, Vol.115 (2005), 201-218
• Centers of convex subsets of buildings. Ann. Global Anal. Geom., Vol.28 (2005), 201-209 (with Andreas Balser)
• Rigidity of spherical buildings and joins. Geom. Funct. Anal., Vol.15 (2005), 720-752
• On Hoelder continuous Riemannian and Finsler metrics. Trans. Amer. Math. Soc., Vol. 358 (2006), 2917-2926 (with Asli Yaman)
• Building-like spaces. J. Math. Kyoto Univ., Vol. 46 (2006), 789-805 (with Andreas Balser)
• Affine functions on $CAT(\kappa )$ spaces. Math. Z., Vol. 255 (2007), 231-244 (with Viktor Schroeder)
• Spaces with many affine functions Proc. Amer. Math. Soc., Vol. 135 (2007), 2263-2271 (with P. Hitzelberger)
• Variationally complete actions on nonnegatively curved manifolds. Illinois J. Math., Vol.51 (2007), 605-615 (with G. Thorbergsson)
• Tangent spaces and Gromov-Hausdorff limits of subanalytic spaces. J. Reine Angew. Math., Vol. 608 (2007), 1-15 (with Andreas Bernig)
• Non-positive curvature and the Ptolemy inequality. Int. Math. Res. Not., no. 22 (2007), Art. ID rnm100 (with Thomas Foertsch and Viktor Schroeder)
• The de Rham decomposition theorem for metric spaces. Geom. Funct. Anal., Vol. 18 (2008), 120-143 (with Thomas Foertsch)
• Notes on the Jacobi equation. Differential Geom. Appl., Vol. 27 (2009), 329-334
• Singular Riemannian foliations on spaces without conjugate points. Proceedings of VIII International Colloquium on Differential Geometry (2009), 75-82
• Curvature explosion in quotients and applications. J. Differential Geom. 85 (2010), 117-140 (with Gudlaugur Thorbergsson)
• Geometric resolution of singular Riemannian foliations. To appear in Geom. Dedicata
• At infinity of finite-dimensional $CAT(0)$ spaces. Math. Ann., Vol. 346 (2010), 1-21 (with Pierre-Emmanuel Caprace)
• Struktur der Submetrien. (Part of the Ph.D. thesis)