Yuval Emek Shay Kutten Mordechai Shalom Shmuel Zaks Hierarchical b-Matching. 189-202 2021 SOFSEM https://doi.org/10.1007/978-3-030-67731-2_14 conf/sofsem/2021 db/conf/sofsem/sofsem2021.html#EmekKSZ21