1. ISLA; University of Amsterdam; Science Park 904; 1098; XH; Amsterdam; The Netherlands
2. Department of Electrical Engineering and Computer Science; University of Stavanger; NO-4036; Stavanger; Norway
3. Royal School of Library Information Science; Birketinget 6; DK-2300; Copenhagen; Denmark
4. Faculty of Arts; CIW-Bedrijfscommunicatie; Radboud University Nijmegen; P.O. Box 9103; NL-6500; HD; Nijmegen; The Netherlands