Products & Materials Products & Materials Science 06 Oct 1989:Vol. 246, Issue 4926, pp. 143DOI: 10.1126/science.246.4926.143 Article Info & Metrics eLetters PDF This is a PDF-only article. The first page of the PDF of this article appears above.
Science Vol 246, Issue 492606 October 1989 Table of Contents Print Table of Contents Back Matter (PDF) Ed Board (PDF) Front Matter (PDF)