Lower bounds on the size of CFGs for specific finite languages
A kind reviewer sent me a paper which proves exactly the same lower bound I do, in exactly the same way. The paper is


  K. Ellul, B. Krawetz, J. Shallit, M.-w. Wang, Regular expressions: new results and open problems, J. Autom. Lang. Comb. 10 (2005), 407–432.


The result is Theorem 30 in the paper.