CREATE TABLE table_51034 ("Date" TEXT, "Series" TEXT, "Circuit" TEXT, "City / State" TEXT, "Winner" TEXT, "Team" TEXT)

What is the circuit on 19 Apr with Craig Lowndes as the winner?
SELECT "Circuit" FROM table_51034 WHERE "Winner" = 'craig lowndes' AND "Date" = '19 apr'
SELECT "Circuit" FROM "table_51034" WHERE "Date" = '19 apr' AND "Winner" = 'craig lowndes'