Partial converse for a relay channel

A special case of the general discrete memoryless relay channel is studied. This channel consists of an input x, a relay output z, a channel output y, and a noiseless channel of capacity C_r allowing the relay sender to send additional information to the decoder. The channel is described by a collection of distributions {p(y, z|x)}. The decoder uses the channel output y and a function f(z) of the relay output at a rate no greater than C_r to recover the message. Some results on the capacity of the channel are obtained