  Theorem~ 4.1 in the 2011 paper "A Framework for Control System Design Subject
to Average Data-Rate Constraints" allows one to lower bound average operational
data rates in feedback loops (including the situation in which encoder and
decoder have side information). Unfortunately, its proof is invalid.
  In this note we first state the theorem and explain why its proof is flawed,
and then provide a correct proof under weaker assumptions.
