The four colour theorem Geometry and topology index History Topics Index The Four Colour Conjecture first seems to have been made by Francis Guthrie. He was a student at University College London where he studied under De Morgan. After graduating from London he studied law but by this time his brother Frederick Guthrie had become a student of De Morgan. Francis Guthrie showed his brother some ...

Introduction to graph theory, with examples.

Graph and Digraph Glossary A | B | C | D | E | F | G | H | I-J | K | L | M | N | O | P-Q | R | S | T-U | V-Z Acyclic Digraph A digraph is acyclic if it contains no cycles. Arc A directed edge of a digraph. Some authors use it as a synonym for an edge of a graph. Other synonyms for arc in a digraph are arrow, directed line, directed edge, and directed link. Arc List A representation of a digraph ...