Digital BW, The Print

I stumbled across a reference the other day on the MIS web site to an article on adding color toner (Pigment I presume) to carbon inks in order to control print tone. The link to that article was broken however, and I have not been able to find it again.
Does anyone know about/have this article? Any and all information about adding color pigment to a carbon ink set would be greatly appreciated.

dk