user: Question: When was the marriage of the person who died on 17 December 1471?
Columns: ['Name', 'Father', 'Birth', 'Marriage', 'Became Countess', 'Ceased to be Countess', 'Death', 'Spouse']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Margaret of Bavaria', 'Albert I, Duke of Bavaria ( Wittelsbach )', '1363', '12 April 1385', "21 March 1405 husband's accession", "10 September 1419 husband's death", '23 January 1423', 'John']
SQL:

assistant: SELECT "Marriage" FROM "Table" WHERE "Death" = '17 December 1471';