Pettit, K. L., and C. S. Bozman. “Toward Increasing Fund-Raising Efficiency: An Exploratory Study Of Use Of The Referral Method By A Non-Profit Organization”. Journal of Applied Business Research (JABR), vol. 7, no. 2, Apr. 1991, pp. 75-81, doi:10.19030/jabr.v7i2.6247.