The link is returning a 403 now (perhaps too much traffic from this article).

For anyone that still wants to read it, here's a citation -- you can easily find a copy by searching for the title of the paper.

  Bacon, David F., Perry Cheng, and V. T. Rajan.
  "A Unified Theory of Garbage Collection."
  Convergence 6, no. 17 (2004): 32.