Book (Yin.2008)
Yin, R. K.
Case Study Research: Design and Methods
Sage Publications, 2008

Book (George.2005)
George, A. L. & Bennett, A.
Case Studies and Theory Development in the Social Sciences
MIT Press, 2005

Article (april05lund)
Lund, B.; Hammond, T.; Flack, M. & Hannay, T.
Social Bookmarking Tools (II): A Case Study - Connotea
D-Lib Magazine, 2005, 11