Cavalier-Smith, T. (2004),
Only six kingdoms of life Proceedings of the Royal Society B: Biological Sciences, 271: 1251–62, doi:10.1098/rspb.2004.2705, PMC 1691724 Freely accessible, PMID 15306349, retrieved 2010-04-29
Whittaker, R. H. (January 1969). New concepts of kingdoms of organisms. Science. 163 (3863): 150–60. Bibcode:1969Sci...163..150W. doi:10.1126/science.163.3863.150. PMID 5762760.
Woese, C. R.; Balch, W. E.; Magrum, L. J.; Fox, G. E.; Wolfe, R. S. (August 1977). An ancient divergence among the bacteria. Journal of Molecular Evolution. 9 (4): 305–311. doi:10.1007/BF01796092. PMID 408502.
Cavalier-Smith, T. (2004),
Only six kingdoms of life Proceedings of the Royal Society B: Biological Sciences, 271: 1251–62, doi:10.1098/rspb.2004.2705, PMC 1691724 Freely accessible, PMID 15306349, retrieved 2010-04-29
Ruggiero, Michael A.; Gordon, Dennis P.; Orrell, Thomas M.; Bailly, Nicolas; Bourgoin, Thierry; Brusca, Richard C.; Cavalier-Smith, Thomas; Guiry, Michael D.; Kirk, Paul M.; Thuesen, Erik V. (2015).
A higher level classification of all living organisms. PLOS ONE. 10 (4): e0119248. doi:10.1371/journal.pone.0119248. PMC 4418965 Freely accessible. PMID 25923521.