The U.S. Supreme Court has agreed to decide "[w]hether a defendant seeking removal to federal court is required to include evidence supporting federal jurisdiction in the notice of removal, or is alleging the required 'short and plain statement of the grounds for removal' enough?"  See here (for the question presented) (Dart Cherokee Basin Operating Company, LLC v. Owens, Case No. 13-719).  The case involves a royalty class action originally filed in state court in Kansas.