“…In particular, for continuous valuations invariant with respect to the special linear group SL(d), i.e., the group of linear transformations with determinant 1, he showed that the only examples are linear combinations of the Euler characteristic and volume. The difficult problem of classifying continuous, rotation invariant valuations on the space of convex bodies was solved by Alesker [2], [3]. In his proof, he approximated continuous, rotation invariant valuations by polynomial valuations and then classified the latter, making use of representations of the orthogonal group.…”