Question: "Back in the U.S.S.R." is a 1968 song by the Beatles, it is credited to the songwriting partnership Lennon–McCartney, but written by who?
Context: "Back in the U.S.S.R." is a 1968 song by the Beatles. "Penny Lane" is a song by the Beatles.  It was written primarily by Paul McCartney but credited to the Lennon–McCartney songwriting partnership.  The lyrics refer to a real street in Liverpool, England. "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". "Tip of My Tongue" is a single by Tommy Quickly backed by The Remo Four.  Written by Paul McCartney and attributed to the songwriting partnership of Lennon–McCartney, it was one of their relatively few songs that were never officially released by the Beatles.  Several takes of this song were apparently recorded on 26 November 1962 at EMI Studios, although George Martin was dissatisfied with the results.  This session has yet to emerge on any of the Beatles bootlegs. "Norwegian Wood (This Bird Has Flown)" is a song by the English rock band the Beatles.  It was written by the songwriting partnership of John Lennon and Paul McCartney and was first released on the album "Rubber Soul" on 3 December 1965.  Musically influenced by the introspective lyrics of Bob Dylan, "Norwegian Wood" is considered a milestone in the Beatles' progression as complex songwriters.  In addition, the recordings of studio musicians during the "Help! " filming sessions, and Ravi Shankar inspired lead guitarist George Harrison to incorporate the sitar into the song. "Hello Little Girl" is the first song written by John Lennon, and credited to the Lennon–McCartney songwriting partnership.  According to Lennon, he drew on an old "Thirties or Forties song" that his mother sang to him.  Written in 1957, it was used as one of the songs at the Beatles unsuccessful Decca audition in 1962.  They recorded a home demo of it, with Stuart Sutcliffe on bass, which is available only on bootleg currently. Ivan Vaughan (18 June 1942 – 16 August 1993) was a boyhood friend of John Lennon, and later schoolmate of Paul McCartney at the Liverpool Institute, both commencing school there in September 1953.  He was born on the same day as McCartney in Liverpool.  He played bass part-time in Lennon's first band, The Quarrymen, and was responsible for introducing Lennon to McCartney at a community event (the Woolton village fête) on 6 July 1957, where The Quarrymen were performing.  McCartney impressed Lennon, who invited McCartney to join the band, which he did a day later.  This led to the formation of Lennon and McCartney's songwriting partnership, and later of The Beatles. Lennon–McCartney was the songwriting partnership between English musicians John Lennon (9 October 19408 December 1980) and Paul McCartney (born 18 June 1942) of the Beatles.  It is one of the best known and most successful musical collaborations in history, with the Beatles selling over 600 million records, tapes and CDs as of 2004.  Between 1962 and 1969, the partnership published approximately 180 jointly credited songs, of which the vast majority were recorded by the Beatles, forming the bulk of their catalogue. "Strawberry Fields Forever" is a song by the English rock band the Beatles.  The song was written by John Lennon and credited to the Lennon–McCartney songwriting partnership.  It was inspired by Lennon's memories of playing in the garden of Strawberry Field, a Salvation Army children's home near where he grew up in Liverpool. "No Reply" is a song by the English rock band the Beatles from their 1964 album "Beatles for Sale".  In North America, it was issued on Capitol Records' variant on the British release, "Beatles '65".  The song was written mainly by John Lennon and credited to Lennon–McCartney.  Lennon originally gave the song to another artist managed by Brian Epstein, Tommy Quickly, in June 1964, but Quickly decided not to use it.  The Beatles recorded the track in London soon after returning from their first full tour of the United States.  The lyrics typify Lennon's more introspective and mature songwriting on the "Beatles for Sale" album.
Answer: Paul McCartney