Indeed a simple inspection of the graph readily suggests the different steps of the reduction which are carried out by elementary transformations, by loop elimination, or by the use of a reduction formula . | Robichaud | Signal flow graphs and applications, 1962 }}
12.
The elementary transformations [ defined by Robichaud in his Figure 7.2, p . 184 ] and the loop reduction permit the elimination of any node " j " of the graph by the " reduction formula " : [ described in Robichaud's Equation 7-1 ].
13.
With the reduction formula, it is always possible to reduce a graph of any order . . . [ After reduction ] the final graph will be a cascade graph in which the variables of the sink nodes are explicitly expressed as functions of the sources.
