Embley, T., R. Hirt, and D. Williams: "Biodiversity at the Molecular Level: The Domains, Kingdoms and Phyla of Life," Philosophical Transactions of the Royal Society of London, Series B, Biological Sciences vol. 344, page 21 ff, 1994. The journal may be challenging to find for such a brief discussion, but it provides a look at the big picture of kingdom phylogeny.

Knowlton, N.: "Confusion of Kingdoms," Nature, vol. 359, page 488, October 8, 1992. How many kingdoms are there really? It depends on whom you talk to.

May, R.: "How Many Species Inhabit the Earth?" Scientific American, October 1992, pages 42–48. A good guess at how many species exist now, how they got here, and the implications for conservation.

McDermott, J.: "A Biologist Whose Heresy Redraws Earth’s Tree of Life," Smithsonian, August 1989, pages 72–80. This article explores Lynn Margulis’s innovative approach to endosymbiosis which has revolutionized the way we think about organisms.

Nikoh, N., N. Hayase, N. Iwabe, and K. I. Kuma: "Phylogenetic Relationship of the Kingdoms Animalia, Plantae and Fungi, Inferred from 23 Different Protein Species," Molecular Biology and Evolution, vol. 11, page 762, 1994. An interesting look at the use of molecular data as taxonomic characters.

Wayne, R. and J. Gittleman: "The Problematic Red Wolf," Scientific American, July 1995, pages 36–39. Is the red wolf a species or a long-established hybrid of the grey wolf and the coyote?

Woese, C.: "Default Taxonomy: Ernst Mayer’s View of the Microbial World," Proc. Natl. Acad. Sci. US, vol 95, 1998,
pages 11043–11046. A spirited defense of the domain system of classification, contrasting fundamentally different views of the basic nature of biological classification, and in doing so revealing so much about the current excitement among taxonomists.