Products & Materials Products & Materials Science 02 Nov 1990:Vol. 250, Issue 4981, pp. 704DOI: 10.1126/science.250.4981.704 Article Info & Metrics eLetters PDF This is a PDF-only article. The first page of the PDF of this article appears above.
Science Vol 250, Issue 498102 November 1990 Table of Contents Print Table of Contents Back Matter (PDF) Ed Board (PDF) Front Matter (PDF)