Andreas M. Chwatal, Günther R. Raidl, Karin Oberlechner. Solving an Extended Minimum Label Spanning Tree Problem to Compress Fingerprint Templates. Journal of Mathematical Modelling and Algorithms, volume 8, number 3, pages 293-334, 2009. (Note: previous technical report version at https://www.ac.tuwien.ac.at/files/pub/chwatal-08a.pdf)