Full Text
The Full Text of this article is available as a PDF (26.9 KB).
. 1987 Mar 1;165(3):937.
Correction
This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).
PMCID: PMC2188271