from http://franinst.sbu.edu/filib/francis.htm

references

     Some of the recent
     works which discuss contemporary ecological concerns and
     Francis's reverence for creation include: Michael W. Fox's St.
     Francis of Assisi, Animals and Nature (Washington, D.C.:
     Center for Respect of Life and Environment, 1989), Roger D.
     Sorrell's St. Francis of Assisi and Nature: Tradition and
     Innovation in Western Christian Attitudes Toward the
     Environment (New York: Oxford U. Press, 1988) and St. Francis
     of Assisi: Patron of the Environment by Warren G. Hansen
     (Chicago: Franciscan Herald Press, 1971).