The Beatles (album) stereo only. In the UK, the following album, "Yellow Submarine", was the last to be shipped in mono. The mono version of "The Beatles" was made available worldwide on 9 September 2009, as part of "The Beatles in Mono" CD boxed set. A reissue of the original mono LP was released worldwide in September 2014. The album's sleeve was designed by pop artist Richard Hamilton, in collaboration with McCartney. Hamilton's design was in stark contrast to Peter Blake's vivid cover art for "Sgt. Pepper's Lonely Hearts Club Band", and consisted of a plain white sleeve. The band's name, in Helvetica,
Sgt. Pepper's Lonely Hearts Club Band idea convincing to most ears." Author Martina Elicker similarly writes that, despite earlier examples, it was "Sgt. Pepper" that familiarised critics and listeners with the notion of a "concept and unified structure underlying a pop album", thus originating the term "concept album". Carys Wyn Jones locates "Pet Sounds" and "Sgt. Pepper" to the beginning of art rock; Julien considers the latter a "masterpiece of British psychedelia". According to historian David Simonelli, "Sgt. Pepper" established the standard for rock musicians, particularly British acts, to strive towards in their self-identification as artists rather than pop stars, whereby, as in the Romantic tradition,