user: Question: Which Semi finalists had a Week of May 15?
Columns: ['Tournament', 'Surface', 'Week', 'Winner', 'Finalist', 'Semi finalists']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Tokyo', 'Carpet (i)', 'January 31', 'Martina Hingis 6–3, 7–5', 'Sandrine Testud', 'Chanda Rubin Katarina Srebotnik']
SQL:

assistant: SELECT "Semi finalists" FROM "Table" WHERE "Week" = 'May 15';