While the terms 'refrain' and 'chorus' often are used synonymously, it has been suggested to use 'refrain' exclusively for a recurring line of identical text and melody which is part of a formal section—an A section in an AABA form (as in I Got Rhythm: "...who could ask for anything more?") or a verse (as in Blowing in the Wind: "...the answer my friend is blowing in the wind")—whereas 'chorus' shall refer to a discrete form part (as in Yellow Submarine: "We all live in a..."). According to the musicologists Ralf von Appen and Markus Frei-Hauenschild,