Mario Ruthmair, Günther R. Raidl. A Layered Graph Model and an Adaptive Layers Framework to Solve Delay-Constrained Minimum Tree Problems. Fifteenth Conference on Integer Programming and Combinatorial Optimization (IPCO XV) (O. Günlük and G.J. Woeginger), volume 6655 of LNCS, pages 376-388, 2011, Springer, Heidelberg.