00386pab a2200145 454500008004000000100002100040245006500061260000900126300001400135362000800149650001000157700002100167700001700188773003500205180718b2008   xxu||||| |||| 00| 0 eng d  aHelpman, Elhanan  aEstimating trade flows: trading partners and trading volumes  c2008  ap.441-87.  aMay  aTrade  aRubinstein, Yona  aMelitz, Marc  aQuarterly Journal of Economics