ERRATA for Lecture IV:

The following corrections are thanks to Ching-Lun Shih:

Section 2, on BFS:
	-- page 9, the proof that there are NO other kinds of edges
	other than the 4 listed is only valid for the case where G
	is a bigraph.  

Section 4, on Full Depth First Search:
	-- page 12, In the first paragraph of Section 4,
		"VISIT(u)" should be "POSTVISIT(u)"
	-- Page 12, Lemma 1.
	   The statement of the lemma confused u with v.  
	   The correct statement should be:

		Then v is a descendent of u in the DFS tree if and only if
		at the time that u was first seen, there is a white path
		from u to v, i.e., ...