Rom Aschner Matthew J. Katz Bounded-Angle Spanning Tree: Modeling Networks with Angular Constraints. 387-398 2014 ICALP (2) https://doi.org/10.1007/978-3-662-43951-7_33 conf/icalp/2014-2 db/conf/icalp/icalp2014-2.html#AschnerK14