user: Question: What is the symbol when the best fit (WMAP, extra parameter) of –, and a Best fit (WMAP only) is .4 ± .3?
Columns: ['Parameter', 'Symbol', 'Best fit (WMAP only)', 'Best fit (WMAP, extra parameter)', 'Best fit (all data)']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Age of the universe ( Ga )', 't_0', '.4 ± .3', '–', '.7 ± .2']
SQL:

assistant: SELECT "Symbol" FROM "Table" WHERE "Best fit (WMAP, extra parameter)" = '–' AND "Best fit (WMAP only)" = '.4 ± .3';