which river's source mountain is postăvarul massif and it's mouth is valea cetății river ?
SELECT DISTINCT var_uri where brack_open var_uri dbo_sourceMountain dbr_Postăvarul_Massif sep_dot var_uri dbo_riverMouth dbr_Valea_Cetății_River_ attr_open Brașov attr_close sep_dot var_uri a dbo_River brack_close