Question: Which 1968 Beatles' song, which is written by Paul McCartney but credited to the song partnership Lennon-McCarney, opens the double-disc album "The Beatles" and then seques into "Dear Prudence"?
Context: "Dear Prudence" is a song by the English rock group the Beatles from their 1968 album "The Beatles" (also known as "the White Album").  The song was written by John Lennon, and credited to Lennon–McCartney.  Written in India, it was inspired by Prudence Farrow, a sister of actress Mia Farrow, who became obsessive about meditating while practising with Maharishi Mahesh Yogi. "Back in the U.S.S.R." is a song by the Beatles.  It is credited to the songwriting partnership Lennon–McCartney, but written by Paul McCartney.  The song opens the 1968 double-disc album "The Beatles" (also known as the "White Album"), and then segues into "Dear Prudence". Prudence Anne Villiers Farrow Bruns (born January 20, 1948) is an American author, meditation teacher, and film producer.  She is the daughter of film director John Farrow and actress Maureen O'Sullivan, and the younger sister of actress Mia Farrow.  She is the subject of the Beatles song "Dear Prudence". Douglas John "Doug" Parkinson (born 30 October 1946, Waratah, New South Wales) is an Australian pop and rock singer.  He led the band, Doug Parkinson in Focus, from 1968 to 1971.  Their cover version of the Beatles' track, "Dear Prudence" (May 1969), peaked at No. 5 on the "Go-Set" National Top 40.  The follow up single, "Without You" / "Hair" (October), also reached No. 5.  Between 1966 and 1997 he had six hit singles.  Australian musicologist, Ian McFarlane, described how Parkinson "conveyed considerable charisma with his imposing presence, 'Lucifer' beard and gruff, raspy voice.  He also surrounded himself with mature, seasoned musicians who added to his appeal." "Back in the U.S.S.R." is a 1968 song by the Beatles. "Glass Onion" is a song by the Beatles from their 1968 double-album "The Beatles" (also known as the "White Album") primarily written by John Lennon and credited to Lennon–McCartney.  This is the first track on the album to feature Ringo Starr on drums.  Starr briefly left the group during recording sessions for the album and was replaced on drums by Paul McCartney on both "Back in the U.S.S.R." and "Dear Prudence". "I'm So Tired" is a song by the Beatles from their double-disc album "The Beatles" (also known as the "White Album").  It was written and sung by John Lennon, though credited to Lennon–McCartney. "Helter Skelter" is a song by the English rock band the Beatles that was released in 1968 on their self-titled double album, often known as "the White Album".  It was written by Paul McCartney and credited to Lennon–McCartney.  The song was a product of McCartney's attempt to create a sound as loud and dirty as possible.  The Beatles' recording has been noted for its "proto-metal roar" and is considered by music historians to be a key influence in the early development of heavy metal. " Rolling Stone" magazine ranked "Helter Skelter" 52nd on its list of the "100 Greatest Beatles songs". "Martha My Dear" is a song by the Beatles written by Paul McCartney (credited to Lennon–McCartney), which first appeared on the double album "The Beatles" (also known as "the White Album").  McCartney is the only Beatle to perform on the track. "Every Little Thing" is a song by the English rock group the Beatles from their 1964 album "Beatles for Sale".  Credited to Lennon–McCartney, it was written by Paul McCartney, although John Lennon is the more prominent lead vocalist on the recording.  Rather than include the track on the North American version of "Beatles for Sale" (which was titled "Beatles '65"), Capitol Records first issued the song on the June 1965 release "Beatles VI".  The track is an early example of the Beatles' use of non-rock instrumentation on a recording, through the addition of timpani drum over the choruses.
Answer: Back in the U.S.S.R.