Dark Side of the Moon (titled Dark Side of the Moon in the 1993 CD edition) is a concept album by the English progressive rock band Pink Floyd. It was released on 17 March 1973 in the U.S. and 24 March 1973 in the UK.[1]

Led Zeppelin IV is the common, but unofficial name of the untitled fourth album by English rock band Led Zeppelin. It was released on November 8, 1971. It has no official title printed anywhere on the album, but is generally called Led Zeppelin IV after the band's previous three numbered albums. Atlantic Records catalogs have used the names Four Symbols (see below) and The Fourth Album. It has also been referred to as Zoso (which the first symbol appears to spell), Untitled and The Runes.[1] Led Zeppelin guitarist Jimmy Page frequently refers to the album in interviews as "the fourth album" and Led Zeppelin IV,[2][3] while singer Robert Plant thinks of it as "the fourth album, that's it".[4]