The Comments and Addenda section is for short comrnunications which are not of'suclz urgency as to justify publication in Physical Review Letters and are not appropriate for regular Articles. It includes only the following types o f communications: (1) comments on papers previously published in The Physical Review or Physical Review Letters; (2) addenda to papers previously published in The Physical Review or Physical Review Letters, in which the additional information can he presented without the need for writing a complete article.