Article (jaeschke2008tag)
Jäschke, R.; Marinho, L.; Hotho, A.; Schmidt-Thieme, L. & Stumme, G.
Giunchiglia, E. (ed.)
Tag Recommendations in Social Bookmarking Systems
AI Communications, IOS Press, 2008, 21, 231-247

Misc (golder05structure)
Golder, S. & Huberman, B. A.
The Structure of Collaborative Tagging Systems
2005