Page 328 Exercise 1

The precedence relations do not sketch out a partial order, and this is quite apparent if we diagram the relations.  Assuming that v_i < v_j implies that v_i is a predecessor of v_j, the graphic protrayal of the relations is as follows.

As the text states, there can be no partial order, if every node has a predecessor.  This is equivalent to saying that a
partial order exists iff all arrows flow to the right.  As is obvious from the graph above,  all arrows do not flow to the right. Thus, every node has a predecessor.  There is no partial order.