From NPR:
Lennon-McCartney is likely one of the most famous songwriting credits in music. John Lennon and Paul McCartney wrote lyrics and music for almost 200 songs and The Beatles have sold hundreds of millions of albums. The story goes that the two Beatles agreed as teenagers to the joint credit for all songs they wrote, no matter the divide in work.
Over the years, Lennon and McCartney have revealed who really wrote what, but some songs are still up for debate. The two even debate between themselves — their memories seem to differ when it comes to who wrote the music for 1965’s “In My Life.”
If the songwriters’ memories (perhaps tainted by the mind-altering era they were writing in) have failed, how can this mystery ever be solved? Well, we can get by with a little help from math.
Mathematics professor Jason Brown spent 10 years working with statistics to solve the magical mystery.
More here.