Source Wikipedia: Alexis Clairaut
Source Differential Geometry (Wikipedia)
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Source Myers's theorem (Wikipedia)
Source Carathéodory conjecture (Wikipedia)
Source Differential Geometry (Wikipedia)
Source Cartan-Hadamard conjecture (Wikipedia)
Source Cartan-Hadamard theorem, Wikipedia
Source Double bubble theorem - Wikipedia
Source Élie Cartan (Wikipedia)
Source Filling Area Conjecture (Wikipedia)
Source Gaspard Monge, Biography (MacTutor History of Mathematics)
Source Heinrich Maschke, Biography (MacTutor History of Mathematics)
Source Wolfram MathWorld: Hopf Conjecture
Source Joseph Plateau, Biography (MacTutor History of Mathematics)
Source Wolfram MathWorld: Kronecker Delta
Source Laplace-Beltrami Operator (Wikipedia)
Source Manifold (Wikipedia)
Source Michael Atiyah (Wikipedia)
Source Wikipedia: Nicolaas Kuiper
Source Penrose-Hawking singularity theorems (Wikipedia)
Source Wikipedia: Pierre Ossian Bonnet
Source Rauch comparison theorem, Wikipedia
Introduced the Ricci flow, the defining tool of geometric analysis in differential geometry, and developed it into the program that proved the Poincare and geometrization conjectures.
Source MacTutor History of Mathematics Archive
Source Sergei Bernstein, Biography (MacTutor History of Mathematics)
Source Wikipedia: Sumner Byron Myers
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Source Tensor Field (Wikipedia)
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Source Weinstein Conjecture (Wikipedia)
Source Wilhelm Blaschke, Biography (MacTutor History of Mathematics)
Source Wikipedia: Willi Rinow