CREATE TABLE table_4521 ("Home team" TEXT, "Home team score" TEXT, "Away team" TEXT, "Away team score" TEXT, "Venue" TEXT, "Crowd" FLOAT, "Date" TEXT)

Who is the home side when north melbourne is the away side?
SELECT "Home team" FROM table_4521 WHERE "Away team" = 'north melbourne'
SELECT "Home team" FROM "table_4521" WHERE "Away team" = 'north melbourne'