The sources for the life of St. Francis are two lives by Thomas of Celano and the biography by St. Bonaventure. Later medieval works are the Legenda trium sociorum, the Sacrum commercium, and the Speculum perfectionis. The Italian Fioretti di San Francesco [little flowers of St. Francis], a series of short anecdotes, has always been popular for its picture of St. Francis and his companions. It exemplifies in simplest form his love of nature and of humanity, a love so great that he preached one time to the sparrows at Alviano (he is often depicted in art preaching to the birds). His spirit also breathes in the Cantico del sole [hymn of the sun], which he may have written, and in the rules for his orders. Artistic and literary representations of St. Francis are innumerable; see L. Cunningham, comp., Brother Francis (1972); biographies by G. K. Chesterton (1924), J. H. Smith (1972), A. House (2001), V. Martin (2001), A. Vauchez (2009, tr. 2012), and A. Thompson (2012); study by E. A. Armstrong (1973).