Before revision: Modern applications include two computerized tutoring systems, ALEKSIntroduction to Knowledge Spaces: Theory and Applications, Christof Körner, Gudrun Wesiak, and Cord Hockemeyer, 1999 and 2001. and the defunct URL
After revision: Modern applications include two computerized tutoring systems, ALEKSIntroduction to Knowledge Spaces: Theory and Applications, Christof Körner, Gudrun Wesiak, and Cord Hockemeyer, 1999 and 2001. and the defunct RATH.