Ararat Harutyunyan Michael Lampis Nikolaos Melissinos Digraph Coloring and Distance to Acyclicity. 986-1013 2024 August 68 Theory Comput. Syst. 4 https://doi.org/10.1007/s00224-022-10103-x db/journals/mst/mst68.html#HarutyunyanLM24 streams/journals/mst