These are just some I had lying around the place 
Coggan, A..R., & Coyle, E.F. (1988). Effect of carbohydrate feedings during high-intensity exercise. Journal of Applied Physiology, 65(4), 1703-1709.
Jacobson, T.L., Febbraio, M.A.., Arkinstall, M.J., & Hawley, J.A. (2000). Effect of caffeine co-ingested with carbohydrate or fat on metabolism and performance in endurance-trained men. The Physiological Society, 86(1), 137-144.
Jentjens, R.L.P.G., & Jeukendrup, A..E. (2005). High rates of exogenous carbohydrate oxidation from a mixture of glucose and fructose ingested during prolonged cycling exercise. British Journal of Nutrition, 93, 485-492.
Yeo, S.E., Jentjens, R.L.P.G., Wallis, G.A.., & Jeukendrup, A..E. (2005). Caffeine increases exogenous carbohydrate oxidation during exercise. Journal of Applied Physiology, 99, 844-850