"Variations", Time, 1936-09-21, archived from the original on December 15, 2008, retrieved 2008-07-13
as of November 2013 there are 1513 amateur leagues in 41 countries.....These leagues are Leo's heritage. "Letter of Support from Jerry Seltzer". Archived from the original on August 20, 2007. Retrieved 2010-01-29.{{cite web}}: CS1 maint: bot: original URL status unknown (link)