[Oops.] Typo in Exercise 4(b) of Chapter 6

[nitishch]

Please verify that the error is present in the most recent revision before reporting.

Chapter number or note title: Chapter 6

Page number: Page 246

Error description: Exercise 4(b) of Chapter 6 states

a non-root vertex v is a cut vertex of G if and only if at
least one descendant (in T ) of each child of v (in T ) is a neighbor
(in G) of some proper ancestor of v (in T ).

It should be

a non-root vertex v is not a cut vertex of G if and only if at
least one descendant (in T ) of each child of v (in T ) is a neighbor
(in G) of some proper ancestor of v (in T ).