Armstrong, E. A. (1976). Saint Francis, nature mystic: The derivation and significance of the nature stories in the Franciscan Legend. University of California Press.

Armstrong, Edward Allworthy. Saint Francis, Nature Mystic: The Derivation and Significance of the Nature Stories in the Franciscan Legend. Berkeley: University of California Press, 1976.

Armstrong, Edward Allworthy. Saint Francis, Nature Mystic: The Derivation and Significance of the Nature Stories in the Franciscan Legend. University of California Press, 1976.