Gustafson, R. “The Flower and Fruit of Health, Virtue, and Happiness: Inwardness Turned Outward in American Public School Music Instruction from the Early Decades to the Present”. Profesorado, Revista De Currículum Y Formación Del Profesorado, vol. 11, no. 3, Dec. 2007, p. 14, https://revistaseug.ugr.es/index.php/profesorado/article/view/20065.