436354.fig.004a
(a)
436354.fig.004b
(b)
Figure 4: (a) One subnetwork of a feasible acyclic multicast network, in which if we blot out the red color, two encoding nodes v5 and v6 disappear. Here, at least one color path passes through the bold black links; (b) The other subnetwork in which if we blot out red color, two encoding nodes v1 and v3 disappear.