00333pab a2200133 454500008004000000100001900040245005000059260000900109300001400118362000800132650001000140700002000150773002900170180718b2007   xxu||||| |||| 00| 0 eng d  aGhironi, Fabio  aTrade flow dynamics with heterorgeneous firms  c2007  ap.356-61.  aMay  aTrade  aMelitz, Marc J.  aAmerican Economic Review