DiTirro, Frank. "Immunohistochemical studies of spinal peptide and serotonin elements in the North American opossum, Didelphis virginiana : I. The distribution of somatostatin, methionine-enkephalin and serotonin immunireactivities in the spinal cord ... /." Doctoral dissertation, Ohio State University, 1981. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487159643970166Chicago Manual of Style (17th edition)