Their content shouldn't leave any doubt:
Paul McCartney was replaced in the Beatles by William Sheppard.
That happened between 31th of August 1966 (the last concert of The Beatles USA tour) and 20th December 1966, the day or their public reappearance.
The substitute is mentioned, as well, in "Sgt. Pepper's Lonely Hearts Club Band" song from the homonymous album with "Billy Shears" as a nickname.
It is very remarkable the number of tests of legal value to support the thesis on the site.