Johnson, Leonard W. 1990. Poets as Players: Theme and Variation in Late Medieval French Poetry.  Stanford, Calif.: Stanford University Press.

Johnson, Leonard W. 1979. 'Nouviaus dis amoureux plaisans': Variation as Innovation in Guillaume de Machaut. Musique naturelle et musique artificielle: In memoriam Gustave Reese, Le Moyen Français. edited by Mary Beth Winn, 11-28. Montreal: Ceres.