CREATE TABLE "open_era_doubles_finals_3_8" (
  "outcome" text,
  "date" real,
  "tournament" text,
  "surface" text,
  "partner" text,
  "opponents_in_the_final" text
);

Question: Tell me the opponents for runner-up and surface of grass
SQL: SELECT "opponents_in_the_final" FROM "open_era_doubles_finals_3_8" WHERE "outcome"='runner-up' AND "surface"='grass';