ArticlesPolicy Consideration Materials: Some Recent Trends and Issues By Hans H. Landsberg See allHide authors and affiliations Science 20 Feb 1976:Vol. 191, Issue 4228, pp. 637-641DOI: 10.1126/science.191.4228.637 Hans H. Landsberg 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.