Which district has an IUCN of iii and was established in 1998?
CREATE TABLE "list_of_natural_monuments" (
  "reserve" text,
  "district" text,
  "iucn" text,
  "co_management" text,
  "est" real,
  "description" text
);
SELECT "district" FROM "list_of_natural_monuments" WHERE "iucn"='iii' AND "est"=1998;