Page 126

Location: Chapter 12, solution to Problem 11

It is (last sentence)

Hence $C(HR)$ -- or alternatively $R(HR)R$ -- is a warbler.

It should become

Hence $C(H(CC))=C(HR)$ -- or alternatively $R(HR)R$ -- is a warbler.

Short explanation

The added expression, while equivalent by virtue of $R=CC$, is the natural one that is encountered during the derivation hence is quite helpful if made explicit.