“"Love is a promise, love is a souvenir, once given never forgotten, never let it disappear." — frequently attributed to Lennon, but entirely unsourced”

p 127
LOVE (1972)

Translation of the Pervigilium Veneris, written in the time of Julius Caesar, and by some ascribed to Catullus: Cras amet qui numquam amavit; Quique amavit, cras amet.

Source: Every You, Every Me

Source: Before Midnight: A Retelling of Cinderella

"Love Me Tender" (1956), the lyrics of this song are credited to Presley and co-writer Vera Matson, but were primarily written by Matson's husband, Ken Darby, who when asked why he credited his wife as co-writer with Presley replied "Because she didn't write it either."
Disputed

Source: Testimony

Source: Chicago: City on the Make (1951), Chapter 2, ""Are you a Christian?""
Context: [About Chicago:] It's every man for himself in this hired air. / Yet once you've come to be part of this particular patch, you'll never love another. Like loving a woman with a broken nose, you may well find lovelier lovelies. But never a lovely so real.

As quoted in Dig, Plant, and Grow! (2009) by Louise Spilsbury, p. 13
Other

Source: Metamorphoses