user: Question: What is the earliest year built for the ship refurbished earlier than 2013?
Columns: ['Ship name', 'Year built', 'Last refurbished', 'Length', 'Crew', 'Guests', 'Staterooms', 'Comments']
Types: ['text', 'real', 'real', 'text', 'real', 'real', 'real', 'text']
Sample row: ['Viking Akun', 1990.0, 2014.0, '423 feet', 115.0, 210.0, 106.0, 'fully refurbished with suites & veranda staterooms']
SQL:

assistant: SELECT MIN("Year built") FROM "Table" WHERE "Last refurbished" < 2013.0;