Merging source code from different products

Recently, I heard that a paper had been written by someone in California on projects where different products had been merged. The conclusions suggested [perhaps not surprisingly] that as the amount of source code increased, the effort required seemed to grow exponentially. If this is the case, then I'd like to know which side of the curve the Illustra/Informix effort lies. Has anyone heard of this research? Know who the author is? TIA. Akmal B. Chaudhri The City University and Independent Consultant