Products & Materials Products & Materials Science 22 Jun 1990:Vol. 248, Issue 4962, pp. 1566DOI: 10.1126/science.248.4962.1566 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 496222 June 1990 Table of Contents Print Table of Contents Back Matter (PDF) Ed Board (PDF) Front Matter (PDF)