Which Opponents have a Year of 1998–99, and a Team of aston villa?
CREATE TABLE "inter_cities_fairs_cup_uefa_cup_uefa_eur" (
  "year" text,
  "team" text,
  "progress" text,
  "score" text,
  "opponents" text
);
SELECT "opponents" FROM "inter_cities_fairs_cup_uefa_cup_uefa_eur" WHERE "year"='1998–99' AND "team"='aston villa';