Andreas Alpers Peter Gritzmann Lionel Thorens Stability and Instability in Discrete Tomography. 175-186 2000 conf/dagstuhl/2000dig Digital and Image Geometry http://link.springer.de/link/service/series/0558/bibs/2243/22430175.htm db/conf/dagstuhl/dig2000.html#AlpersGT00