The editor appears to have been a Martha Siegel, but I think the simplest solution in your case is to go the table of contents of that issue, and click "Cite this item", which yields citations like
Mixon, Bill, Steven J. Brams, D. Marc Kilgour, Robert Mandl, David L. Farnsworth, and David M. Bloom. "News and Letters." Mathematics Magazine 68, no. 4 (1995): 322-24. http://www.jstor.org/stable/2690589.
for the news and letters section. A three page document is short enough that you don't really need to be more specific than that. Still, if you want you can make it clear in the text that you're only citing the editor's introduction to the section. A less standard solution would be adding something to that effect in brackets in the reference list, e.g. "[Editor's introduction]".