Products & Materials Products & Materials Science 20 Apr 1990:Vol. 248, Issue 4953, pp. 391DOI: 10.1126/science.248.4953.391 Article Info & Metrics eLetters PDF This is a PDF-only article. The first page of the PDF of this article appears above.
Science Vol 248, Issue 495320 April 1990 Table of Contents Print Table of Contents Back Matter (PDF) Ed Board (PDF) Front Matter (PDF)