"Work contributing to this paper was supported by funds from the United Nations Environment Programme, the Food and Agriculture Organization of the United Nations, the Pew Charitable Trusts, and the University of Minnesota."
"This paper is published as contribution no. 19,807 of the Minnesota Agriculture Experiment Station and is a product of Project nos. MN-42-049 and MN-42-035."
"July 1992."
Includes bibliographical references (pages 27-29).