Manfred Droste Doreen Götze Steffen Märcker Ingmar Meinecke Weighted Tree Automata over Valuation Monoids and Their Characterization by Weighted Logics. 30-55 2011 Algebraic Foundations in Computer Science http://dx.doi.org/10.1007/978-3-642-24897-9_2 conf/birthday/2011bozapalidis db/conf/birthday/bozapalidis2011.html#DrosteGMM11