name the common serving line of hofgeismar-hümme railway station and kassel hauptbahnhof ?
SELECT DISTINCT var_uri where brack_open dbr_Hofgeismar-Hümme_railway_station dbo_servingRailwayLine var_uri sep_dot dbr_Kassel_Hauptbahnhof dbo_servingRailwayLine var_uri brack_close