CREATE TABLE "prime_ministers_of_iceland_1917_present" (
  "entered_office" text,
  "left_office" text,
  "party" text,
  "election" text,
  "coalition" text
);

Question: When did the party elected in jun. 1959 enter office?
SQL: SELECT "entered_office" FROM "prime_ministers_of_iceland_1917_present" WHERE "election"='jun. 1959';