Bicycling Science, 3rd Edition.
Assuming that you could fine a wider and a narrower tire with the EXACT same weight, the EXACT same suppleness, and then pumped them up to the EXACT same pressure, the wider tire would offer less rolling resistance. Unfortunately, this is never the case. Reality is a *****. The best compromise generally runs between 700x23c and 700x28c depending on the aerodynamics demanded by the application.