Mary Schmich (2012). “The Best of Mary Schmich: Selected Writings by the Chicago Tribune's Winner of the 2012 Pulitzer Prize for Commentary”, p.32, Agate Digital
Claude Debussy's instructions to the singers in his opera "Pelléas et Mélisande", as quoted in Henry William Simon "100 Great Operas and Their Stories" (p. 371), 1989.