user: Question: What was the archive for episode with 6.6 million viewers?
Columns: ['Episode', 'Broadcast date', 'Run time', 'Viewers (in millions)', 'Archive']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['" Episode 1 "', '14September1968', '21:27', '6.6', '16mm t/r']
SQL:

assistant: SELECT "Archive" FROM "Table" WHERE "Viewers (in millions)" = '6.6';