• Cladistics - The International Journal of the Willi Henning Society - Covers theory, method, the philosophical aspects of systematics, and the role of systematic and evolutionary studies in the investigation of biogeographical and other general biological phenomena.
• What is Cladistics? - The methods and terminology of phylogenetic systematics explained by the magazine Fossil News.
• Introduction to Cladistics - Cladistics is a particular method of hypothesizing relationships among organisms based on the idea that members of a group share a common evolutionary history.
• Willi Hennig Society - Society of scientists studying cladistics.
• The Compleat Cladist: A Primer of Phylogenetic Procedures - A book in PDF-format, about the basics of cladistics.
• Understanding Cladistics - Short introduction from the American Museum of Natural History.
• Phylogenetics Methodology - Introduction to various phylogenetic statistical methodologies.