An oversight in Guaspari and Solovay’s “Rosser sentences” [D. Guaspari, R.M. Solovay, Rosser sentences, Annals of Mathematical Logic 16 81–99] is pointed out and emended. It concerns the premisses of their proof that there are standard proof predicates all of whose Rosser sentences are provably equivalent. The result holds up, but the premisses mentioned in the paper have to be strengthened somewhat.

This volume succeeds the same authors' well-known An Introduction to Modal Logic and A Companion to Modal Logic. We designate the three books and their authors NIML, IML, CML and H&C respectively. Sadly, George Hughes died partway through the writing of NIML.