1David MeArthur. Sustainability Issues and Activities for the NSDL.(2003). http : //esdl . eomputer . org/eomp/proceedings/jcdl/ 2003/1939/00/19390395. pdf.
2Library of Congress. National Digital Information Infrastructure and Preservation Program. (2003) .http ://www. digitalpreservation, gov/index, php.
3Wittenberg K. Business Models for the NDSL: Issues for Discus sion. (2002). http ://sustain. comm. nsdlib, org/doc-tracker/docs-download, php?id = 354.
4CLIR. Building and Sustaining Digital Collections: Models for Libraries and Museums. (2001) . http ://www. clir. org/pubs/reports/pub 100/pub 100. pdf.
5Smith A. Issues in Sustainability: Creating Value for Online Users. (2003). http://www.firstmonday.dk/issues/issue8-5/smith/index, html.
3Twidale M B, Nichols D M. Using Studies of Collaborative Activity in Physical Environments to Inform the Design of Digital Libraries. Presented at the CSCW'98 Workshop Collaborative and Co-openltive Information Seeking in Digital Information Environments 1998.
4Proctor R, Goldenberg A, Davenport E. Genres in Support of Collaborative Information Retrieval in the Virtual Library. Interacting with Computers, 1998, 10(2):157~175.
5Nardi B, Miller J. Twinkling Lights and Nested Loops: Distributed Problem Solving and Spreadsheet Development. International Journal of Man-Machine Studies, 1991, 34(2).
6Rodden T, Mariani J A , Blair G S. Supporting Cooperative Applications. Computer Supported Cooperative Work, 1992, 1(1).
7Root R W. Design of a Multi-media Vehicle for Social Browsing Proceedings of the Conference on Computer-Supported Cooperative Work (CSCW 88), 1988.
8Wilson T D. On User Studies and Information Needs. Journal of Documentation, 1981, 37 (1).
9Sheperd J. The Information Needs and Information Seeking Behaviour of Polytechnic History Lecturers. Report Number: #5743, British Library Research and Development Department,1983.
10Fox E A, Hix D, Nowell L T, Brueni D J, Wake W C, Heath L S, Rao D Users, User Interfaces, and Objects-Envison, a digital library. Journal of the American Society for Information Science, 1993, 44(8): 480~491.