Write a SQL select statement to identify the individuals who are listed as authors of each and every book in relation A. The expected result for the given database instance is: |------| | aid | |------| | Carl | |------| Make sure to adopt the same output-schema. Test your query in sqlfiddle.com, using PostGRES 9.6 and some arbitrary instance of table A. The relation produced by your query should always be a set.