Florin O. Bilbiie, Fabio Ghironi, and Marc J. Melitz. "Endogenous Entry, Product Variety, and Business Cycles." Journal of Political Economy 120 (2012), 304-45.
Paper available at: http://faculty.washington.edu/ghiro/BGMRBCJPE12.pdf
Paper available at: http://faculty.washington.edu/ghiro/BGMRBCJPE12.pdf