Spaces with non-positive curvature

Symbolic Dynamics

Marston Morse, Gustav A. Hedlund · American Journal of Mathematics · 1938 · 427 citations

The Isoperimetric Problem in the Minkowski Plane

Herbert Busemann · American Journal of Mathematics · 1947 · 84 citations

Integral Geometry, Global Geometry, Engineering +9

Intrinsic Area

Herbert Busemann · Annals of Mathematics · 1947 · 64 citations

Local metric geometry

Herbert Busemann · Transactions of the American Mathematical Society · 1944 · 48 citations · Full text