[1] Hughes, Arthur Middleton, "Measuring the Loyalty Effect," Direct Magazine, 1998
doi.org
Gunnarsson, Claes; Jonsson, Seth (2003). "Charge the relationships and gain loyalty effects: Turning the supply link alert to IT opportunities". European Journal of Operational Research. 144 (2): 257–269. doi:10.1016/S0377-2217(02)00392-2.
