McGinnis, L. M., M. R. Widmer, C. L. Wright, T. M. Parr, and H. H. Stein. 2007. Site of activity within the digestive tract of growing pigs of an evolved E.coli-derived and a fungal-derived commercial phytase. J. Anim. Sci. 85(Suppl. 2):87 (Abstr.)  Link to abstract (.pdf)