00371nam a2200109Ia 4500008004100000082002300041100001900064245005700083260003600140300002300176440006200199251203b        |||||||| |||| 00| 0 eng d  a309.50184bEr69.OS  aErlander, Sven  aOptimal spatial interaction and the gravity modelb/  aBerlin:bSpringer-Verlag,c1980  a107p. Index, Bibl.  aLecture notes in Economics and Mathematical Systems ; 173