When wikipedia and the other bits of the web start pointing at pay walls and I have few good pointers I actually go to an academic library. The magic is that there you can get through most of the pay walls without actually paying. You also find out who cited that work, which would normally also cost money but does not. (This may be a function of the pay walls I tend to run into.)
Given that Karsten went to a *university* library in the late 1990s it is slightly surprising he did not have access to a good range of online journals. I know that a complete range of monographs and conference proceedings is largely restricted to libraries that have a legal right to a free copy.
Hopefully IV's patent will means that the manufacturers of 3D printers do not implement DRM to avoid patents in that area.