Comparative Genomics of the Archaea (Euryarchaeota): Evolution of Conserved Protein Families, the Stable Core, and the Variable Shell - Makarova, Kira S.; Aravind, L.; Galperin, Michael Y.; Grishin, Nick V.; Tatusov, Roman L.; Wolf, Yuri I.; Koonin, Eugene V. (Genome Research, 1999)