Granular Activated Carbon In The Reef Tank: Fact, Folklore And Its Effectiveness In Removing Gelbstoff By: Richard Harker (Be sure to check out the graph at the end, it has some surprising results. The carbon's on the right performed the best). http://www.pets-warehouse.com/carbon.htm

Activated Carbon By: Steve Kvech and Erika Tull (This article contains some incredible macro images that help to understand how much surface area carbon really contains).  http://www.cee.vt.edu/ewr/environmental/teach/wtprimer/carbon/sketcarb.html

An Overview of Activated Carbon in the Marine Tank By: James R. Layton www.hallman.org/filter/gac.html

Activated Carbon By: Andreas Iliopoulos, John G. Reclos and George J. Reclos www.malawicichlidhomepage.com/aquainfo/activated_carbon.html