“…Projection bodies and intersection bodies play a critical role in the solution of Shephard's problem, respectively the Busemann-Petty problem. We refer the reader to [16], [17], [33], [5], [4], [9], [10], [12], [13], [14], [18], [19], [20], [23], [22]. The projection body operator and intersection body operator are continuous and GL(n) contravariant valuations, see [16], [17].…”