user: Question: What Nation of citizenship has a Stock car vehicle with a year of 1999?
Columns: ['Year', 'Driver', 'Nation of citizenship', 'Racing series', 'Type of vehicle']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [1993.0, 'Nigel Mansell', 'United Kingdom', 'Formula One', 'Open wheel']
SQL:

assistant: SELECT "Nation of citizenship" FROM "Table" WHERE "Type of vehicle" = 'Stock car' AND "Year" = 1999.0;