Röller, N., & Zielinski, S. On the Difficulty to Think Twofold in One: Nils Röller. Siegfried Zielinski. Sciences of the interface : proceedings of the International Symposium Sciences of the Interface, ZKM, Center for Art and Media, Karlsruhe Germany, May 18-21, 1999.(2001).

Röller, Nils, and Siegfried Zielinski. "On the Difficulty to Think Twofold in One: Nils Röller. Siegfried Zielinski." Sciences of the Interface : Proceedings of the International Symposium Sciences of the Interface, ZKM, Center for Art and Media, Karlsruhe Germany, May 18-21, 1999.(2001) .

Röller, Nils, and Siegfried Zielinski. "On the Difficulty to Think Twofold in One: Nils Röller. Siegfried Zielinski." Sciences of the Interface : Proceedings of the International Symposium Sciences of the Interface, ZKM, Center for Art and Media, Karlsruhe Germany, May 18-21, 1999.(2001), .