Uriel Feige Magnús M. Halldórsson Guy Kortsarz Aravind Srinivasan Approximating the Domatic Number. 172-195 2002 32 SIAM J. Comput. 1 http://epubs.siam.org/sam-bin/dbq/article/38075 db/journals/siamcomp/siamcomp32.html#FeigeHKS02