For instance, when a conveyance is made to a man, his assent to it is presumed, for the following reasons; cause there is a strong intendment of law, that it is for a person's benefit to take, and no man can be supposed to be unwilling to do that which is for his advantage. 2.
A simple graph, as opposed to a multigraph, is an undirected graph in which both multiple edges and loops are disallowed. In a simple graph the edges form a set (rather than a multiset) and each edge is an unordered pair of distinct vertices.
A tree is a mathematical structure that can be viewed as either a graph or as a data structure. The two views are equivalent, since a tree data structure contains not only a set of elements, but also connections between elements, giving a tree graph. Trees were first studied by Cayley (1857). McKay maintains a database of trees up to 18 vertices, and Royle maintains one up to 20 vertices.