Invariant differential operators and the range of the radonD-plane transform

The Radon transform on Euclidean spaces, compact two-point homogeneous spaces and Grassmann manifolds

Sigurđur Helgason · Acta Mathematica · 1965 · 302 citations · Full text

Natural Sciences, Computer Science, Computational Geometry +12

Differential operators on homogeneous spaces

Sigurđur Helgason · Acta Mathematica · 1959 · 292 citations · Full text

Natural Sciences, Mathematics, Differential Equations +7

The ultrahyperbolic differential equation with four independent variables

Fritz John · Duke Mathematical Journal · 1938 · 181 citations

Natural Sciences, Mathematics, Physics +9

The Surjectivity of Invariant Differential Operators on Symmetric Spaces I

Sigurđur Helgason · Annals of Mathematics · 1973 · 120 citations

Natural Sciences, Mathematics, Differential Equations +12

Integral geometry in affine and projective spaces

I. M. Gel'fand, Simon Gindikin · Journal of Mathematical Sciences · 1982 · 112 citations

Natural Sciences, Plastic Surgery, Geometry +11