The general limited-angle problem is underdetermined. This in discrete tomography. However, electron microscopy of crystals is a terminology is used in the following theorem. much more specific problem, and is subject to stringent mathematical conditions. Using a constructive argument, we show that under these APPENDIX Matlab Routines. Two Matlab .m files are listed below. The first, gendata.m, takes a matrix (like any of the three phantoms shown in Section II) and the tangent of the angle at which the diagonals are measured. (See Fig. 1 in main text.) gendata.m Phantom 2.returns the diagonal data in a column vector.