- Spektrum der Wissenschaft (10):92-94 (2011)
- IJKL 7(3/4):157-178 (2011)
- J. ACM 31(4):855-878 (1984)
- ICLS 3, page 338-345. International Society of the Learning Sciences, (2008)
- ICLS 3, page 346-353. International Society of the Learning Sciences, (2008)
- ICLS 3, page 360-367. International Society of the Learning Sciences, (2008)
- ICLS 3, page 182-189. International Society of the Learning Sciences, (2008)
- ASIACCS, page 416-422. ACM, (2011)
- Data Compression Conference, page 102-111. IEEE Computer Society, (1992)
- Data Compression Conference, page 239-246. IEEE Computer Society, (1991)
- Data Compression Conference, page 140-149. IEEE Computer Society, (1996)
- Data Compression Conference, page 408-417. IEEE Computer Society, (1998)
- Data Compression Conference, page 131-140. IEEE Computer Society, (1997)
- Data Compression Conference, page 218-227. IEEE Computer Society, (1999)
- Data Compression Conference, page 163-172. IEEE Computer Society, (2000)
- ICML, page 953-960. Omnipress, (2011)
- CSCL, page 573-574. International Society of the Learning Sciences, (2002)
- CSCL, page 717-726. International Society of the Learning Sciences, (2005)
- CSCL, page 125-134. International Society of the Learning Sciences, (2005)
- CSCL, page 13-22. International Society of the Learning Sciences / ACM DL, (2007)


author