Artur Czumaj Miroslaw Kowaluk Andrzej Lingas Faster algorithms for finding lowest common ancestors in directed acyclic graphs. 2006 13 Electronic Colloquium on Computational Complexity (ECCC) http://eccc.hpi-web.de/eccc-reports/2006/TR06-111/index.html 111 db/journals/eccc/eccc13.html#CzumajKL06