The invalidating reference in question was handout material that was freely distributed to 600 students in a class. Additional copies were sold to anyone who asked. Further, the material (textbook) was cited in a number of journal articles and the material was sold to journal readers who contacted the professor about the material.
The patent involved is US 5,930,156, and the re-exam is 90/008,645. A relevant case is TypeRight Keyboard Corp. v. Microsoft Corp., 374 F.3d 1151, 1159 (Fed. Cir. 2004).
See previous IPBiz post on Klopfenstein:
CAFC uses an American Lawyer article as 102(b) art