minor language change
Remove 'Tree'
Create 'Multigraph', and 'Pseudograph'
Add note to 'Incidence Matrix'
minor syntax change
Define 'Incidence Matrix'
Define 'Adjacency Matrix'
Restructure 'Adjacency Lists'
fix minor typo
Provide graphical representation for 'Adjacency Lists'
Define 'Adjacency List'
Create 'Algorithm: Graph Representation'