Research News Looking for the Hard Background By M. M. W. See allHide authors and affiliations Science 25 Jan 1991:Vol. 251, Issue 4992, pp. 381DOI: 10.1126/science.251.4992.381 M. M. W. Find this author on Google Scholar Find this author on PubMed Search for this author on this site Article Info & Metrics eLetters PDF This is a PDF-only article. The first page of the PDF of this article appears above.
Science Vol 251, Issue 499225 January 1991 Table of Contents Print Table of Contents Back Matter (PDF) Ed Board (PDF) Front Matter (PDF)