CREATE TABLE table_75621 ("Source" TEXT, "Date" TEXT, "Goldberg" TEXT, "Murray" TEXT, "Silbert" TEXT, "Undecided" TEXT)

What is the date of the poll with Silbert at 10.0%?
SELECT "Date" FROM table_75621 WHERE "Silbert" = '10.0%'
SELECT "Date" FROM "table_75621" WHERE "Silbert" = '10.0%'