Brian was greatly influenced by "The Four Freshmen", they are good. "Peter, Paul & Mary" , "Seekers", "Simon & Garfunkel", "The Vogues", "The Tokens", "Anita Kerr Singers", "Ray Charles Singers". These just some of the great harmonies Brian would have been listening to in these years.
As for some of BB's other releases I really like, Smile and Surfs Up.