(and Starr's ending scream), and the fade-out of "Yer Blues" is 11 seconds longer on the mono mix. Several songs have missing or different overdubs or effects which differ from the stereo mixes. In the United States, mono records were already being phased out; the US release of The Beatles was the first Beatles LP to be issued in stereo only. In the UK, the Beatles following album, Yellow Submarine, was the last to be issued 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. The original mono LP was rereleased worldwide in September 2014. Songs Side one McCartney wrote "Back in the U.S.S.R." as a parody of Chuck Berry's song "Back in the U.S.A." and the Beach Boys. A field recording of a jet aeroplane taking off and landing was used at the start of the track, and intermittently throughout it. The backing vocals were sung by Lennon and Harrison in the style of the Beach Boys, further to Mike Love's suggestion in Rishikesh that McCartney include mention of the "girls" in the USSR. The track became widely bootlegged in the Soviet Union, where the Beatles' music was banned, and became an underground hit. "Dear Prudence" was one of the songs recorded at Trident. The style is typical of the acoustic songs written in Rishikesh, using guitar arpeggios. Lennon wrote the track about Mia Farrow's sister Prudence Farrow, who rarely left her room during the stay in commitment to the meditation. "Glass Onion" was the first backing track recorded as a full band after Starr's brief departure. MacDonald claimed Lennon deliberately wrote the lyrics to mock fans who claimed to find "hidden messages" in songs, and referenced other songs in the Beatles catalogue – "The Walrus was Paul" refers back to "I Am the Walrus" (which itself refers to "Lucy in the Sky with Diamonds"). McCartney, in turn, overdubbed a recorder part after the line "I told you about the Fool on the Hill", as a deliberate parody of the earlier song. A string section was added to the track in October. "Ob-La-Di, Ob-La-Da" was written by McCartney as a pastiche of ska music. The track took a surprising amount of time to complete, with McCartney demanding perfectionism that annoyed his colleagues. Jimmy Scott, a friend of McCartney, suggested the title and