“…The model in single photon emission tomography [52] involves a Radon line transform with a measure that is not group invariant. Models in radar [56], sonar, and thermoacoustic tomography [1] involve circular, elliptical, or spherical mean transforms and their generalizations, and researchers use harmonic and microlocal analysis, PDEs, and group theory to develop reconstructions methods and properties. There is much elegant mathematics in these areas, but the details are beyond the scope of this review.…”