In a paper Is the null-graph a pointless concept?" Harary and Read examine reasons for assigning certain properties to the empty graph. They observe that from the enumeration perspective it appears to be convenient to consider the empty graph as a forest, but not a tree.
In a paper Is the null-graph a pointless concept?" Harary and Read examine reasons for assigning certain properties to the empty graph. They observe that from the enumeration perspective it appears to be convenient to consider the empty graph as a forest, but not a tree.