@TechReport{CEPII:2008-30,
author={Matthieu Crozet and Pamina Koenig},
title={Structural Gravity Equations with Intensive and Extensive Margins },
year=2008,
month=December,
institution={CEPII},
type={Working Papers},
url={http://www.cepii.fr/CEPII/en/publications/wp/abstract.asp?NoDoc=1067},
number={2008-30},
}