Published in AIP Conference Proceedings, Volume 135, November 25, 1985, pages 576-579.
Copyright © 1985 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article was published in AIP Conference Proceedings.
The definitive version is available at http://dx.doi.org/10.1063/1.35474.