To complete the formulation of the nodal analysis equations, its us apply KCL to all supernodes not containing the reference node and to all other nonreference nodes. This has the effect of reducing the number of node equations by one per supernode. The presence of voltage source thus reduces the number of equation and the number of unknown s in nodal analysis by one per voltage source. For instance, in Fig. 4.13(a) there are five nonreference nodes, and if the voltage sources were all current sources, five nonreference in five unknown would be required. Because there are two voltage sourecs, however, we may break the circuit by using just three equations in three unknowns, as we now demonstrate.