SELECT T2.Author FROM acceptance AS T1 JOIN submission AS T2 ON T1.Submission_ID  =  T2.Submission_ID GROUP BY T2.Author HAVING COUNT(DISTINCT T1.workshop_id)  >  1
Which authors have submitted to more than one workshop?
[Schema (values) (types)]: | workshop_paper |  workshop : workshop_id (text) , date (number) , venue (text) , name (text) | submission : submission_id (text) , scores (number) , author (text) , college (text) | Acceptance : submission_id (text) , workshop_id (number) , result (text);