References

H. Edelsbrunner. Weighted alpha shapes. Technical Report UIUCDCS-R-92-1760, Dept. Comput. Sci., Univ. Illinois, Urbana, IL, 1992.
H. Edelsbrunner and E. P. Mücke. Three-dimensional alpha shapes. ACM Trans. Graph., 13(1):43-72, January 1994.
H. Edelsbrunner. Algorithms in Combinatorial Geometry. Springer-Verlag, Berlin, 1987.
U. Grenader, Abstract Inference. Wiley, New York, 1981.
D. P. Mandal and C. A. Murthy. Selection of Alpha for Alpha-Hull in R². Pattern Recognition, Vol 30, no. 10, pp. 1759-1767, 1997.
E.P. Mucke. Shapes and Implementations in Three-Dimensional Geometry. Ph.D. Thesis, Dept. Computer Science, U. Illinois at Urbana-Champaign. 1993.
C. A. Murthy, On consistent estimation classes of R² in the context of cluster analysis, Ph.D. Thesis, Indian Statistical Institute, Calcutta, India. 1988.
F.P. Preparata and M.I. Shamos. Computational Geometry--An Introduction. Springer-Verlag, New York, 1985.
M. Teichmann and M. Capps. Surface reconstruction with anisotropic density-scaled alpha-shapes. In IEEE Visualization '98 Proceedings , pages 67-72, San Francisco, CA, October 1998. ACM/SIGGRAPH Press.

Alpha Shapes Tutorial
Here is a project from 1997 by François Bélair. Nice applet .
Introduction to Alpha Shapes
Stepping Into Alpha Shapes
This is a nice page on alpha shapes. It has many references to key articles (with links to available ones) and concise descriptions.

Here one can find the other projects for Pattern Recognition 308-644 at McGill University (class of 2002).