@techreport {Petra-et-al08b, title = {Extended and Constrained Cimmino-type Algorithms with Applications in Tomographic Image Reconstruction}, year = {2008}, institution = {IWR, University of Heidelberg}, url = {http://www.ub.uni-heidelberg.de/archiv/8798/}, author = {Stefania Petra and Popa, Constantin and Christoph Schn{\"o}rr} }