Tree based models and algorithms for the preemptive asymmetric Stacker Crane problem Hervé Kerivin, Mathieu Lacroix, Alain Quilliot and Hélène Toussaint RAIRO-Oper. Res., 45 3 (2011) 179-207 Published online: 21 October 2011 DOI: 10.1051/ro/2011110