Table schema:
CREATE TABLE table_name_68 (first_day_cover_cancellation VARCHAR, denomination VARCHAR, date_of_issue VARCHAR)

Question: What's the First Day Cover Cancellation with Denomination of $0.50 and Date of Issue as 13 June 2005?
SQL: SELECT first_day_cover_cancellation FROM table_name_68 WHERE denomination = "$0.50" AND date_of_issue = "13 june 2005"