Journal Article 2 ill-posed problem Algorithms 1 Krylov subspace method 1 Lanczos process 1 Tikhonov functional 1 X-ray tomography 1 mehr ... conjugate-gradient method 1 convolution 1 data encapsulation 1 filter 1 linear equations 1 minimum-residual method 1 pseudoinverse solution 1 regression 1 ring artefacts 1 singular least-squares 1 sparse matrix 1 weniger ...