Intelligent Tutoring Systems 4th International Conference, ITS '98, San Antonio, Texas, USA, August 16-19, 1998, Proceedings - Goettl, Barry P.; Goettl, Barry P.; Halff, Henry M.; Halff, Henry M.; Redfield, Carol L.; Redfield, Carol L.; Shute, Valerie J.; Shute, Valerie J. (Springer Berlin Heidelberg : Imprint: Springer, 1998)