user: Question: What is the ISBN of the book with a first edition in May 2011?
Columns: ['Title', 'Pages', 'First edition', 'Second edition', 'ISBN']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Hardcovers', 'Hardcovers', 'Hardcovers', 'Hardcovers', 'Hardcovers']
SQL:

assistant: SELECT "ISBN" FROM "Table" WHERE "First edition" = 'May 2011';