user: Question: Which stadium is managed by Kari Martonen?
Columns: ['Club', 'Location', 'Stadium', 'Capacity', 'Manager', 'Kitmaker']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['AC Oulu', 'Oulu', 'Castrén', 4000.0, 'Juha Malinen', 'Umbro']
SQL:

assistant: SELECT "Stadium" FROM "Table" WHERE "Manager" = 'Kari Martonen';