user: Question: Which Constructor has the Winning Driver, Jo Siffert?
Columns: ['Race Name', 'Circuit', 'Date', 'Winning driver', 'Constructor', 'Report']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['II Cape South Easter Trophy', 'Killarney', '9 January', 'Paul Hawkins', 'Brabham - Climax', 'Report']
SQL:

assistant: SELECT "Constructor" FROM "Table" WHERE "Winning driver" = 'Jo Siffert';