Darwin, Charles ((1964). ). On the Origin of Species. A Facsimile of the First Edition. Cambridge, Harvard University Press.
Eldredge, Niles (1985). Unfinished Synthesis: Biological Hierarchies and Modern Evolutionary Thought. New York, Oxford University Press.
Eldredge, Niles (1995). Reinventing Darwin: The Great Debate at the High Table of Evolutionary Theory. New York, John Wiley & Sons. The author lays out forcefully the debate between reductionists who strive to reduce all biological phenomena to competition between genes for reproductive success (the so-called ultra-Darwinians) and non-reductionists who argue that each level in the hierarchical organization of life should be studied in its own right. Another fundamental issue in the debate is whether evolution is gradual or punctuated by radical discontinuities.
Eldredge, Niles (1999). The Pattern of Evolution. New York, W. H. Freeman and Company.
Gould, Steven Jay (1977). Ever Since Darwin: Reflections in Natural History. New York, W. W. Norton & Company.
Gould, Steven Jay (1980). The Panda’s Thumb: More Reflections in Natural History. New York, W. W. Norton & Company.
Gould, Steven J. and Niles Eldredge (1977). " “Punctuated Equilibria: the Tempo and Mode of Evolution Reconsidered.”." Paleobiology, 3, (115-151).
Sober, Elliot, Ed (1994). Conceptual Issues in Evolutionary Biology. A Bradford Book. Cambridge, MA, MIT Press. This edited volume contains a superb collection of essays by leading biologists and philosopers of science