We establish a surprising connection between Menger’s classical covering property and Blass-Laflamme’s modern combinatorial notion of groupwise density. This connection implies a short proof of the groupwise density bound on the additivity number for Menger’s property.
"Menger’s covering property and groupwise density." J. Symbolic Logic 71 (3) 1053 - 1056, September 2006. https://doi.org/10.2178/jsl/1154698591