A "--" in the district column means, that the town is a district-free town, i.e. it is by itself a district.
... cysts[?] Arachnoiditis[?] Arakawa'sa syndrome II[?] Arbovirosis[?] Arc syndrome[?] Aredyld syndrome[?] AREDYLD[?] Arginase deficiency[?] Arginemia[?] ...