FIVE WAYS TO COMBINE TANGIBLES WITH INTANGIBLES
This paper presents five different ways to establish weights for the criteria that govern making comparisons. Four of these can be done in the context of the AHP, but the fifth and most reliable one is obtained by using the ANP.
Saaty, T. L. (2000). Fundamentals of decision making and priority theory with the analytic hierarchy process (Vol. 6). Pittsburgh: RWS Publications.