Dolly Parton and Marty Robbins are the latest country artists to be anthologized by Legacy Recordings. The two-CD sets will be released June 28. The Essential Marty Robbins includes 40 songs (including 16 No. 1 hits) spanning his 30-year career, while The Essential Dolly Parton collects 37 tracks from 1967 to 2001. … In related news, Legacy Recordings has postponed the reissues of three Rosanne Cash studio albums until August.