Cassidy, C. M., M. D. Glissmeyer, and C. J. Capps III. “Mapping An Internal-External (I-E) Matrix Using Traditional And Extended Matrix Concepts”. Journal of Applied Business Research (JABR), vol. 29, no. 5, Aug. 2013, pp. 1523-8, doi:10.19030/jabr.v29i5.8033.