Products & Materials Products & Materials Science 01 Sep 1989:Vol. 245, Issue 4921, pp. 996DOI: 10.1126/science.245.4921.996 Article Info & Metrics eLetters PDF This is a PDF-only article. The first page of the PDF of this article appears above.
Science Vol 245, Issue 492101 September 1989 Table of Contents Print Table of Contents Back Matter (PDF) Ed Board (PDF) Front Matter (PDF)