Relationship between multiple and partial coherence functions

The
n
th-order multiple coherence between a stationary random process and
n
other stationary random processes is decomposed into a sum of
n
components consisting of products of lower order partial and multiple coherence functions. An inequality is derived between partial coherence and the ratio of ordinary coherence to multiple incoherence. As a result, a coherency diagram is suggested describing the different coherency functions and their relationships.