def find_samples_sheet doc
      #sheet = doc.find_first("//ss:sheet[@name='SDRF']")
      #sheet = doc.find_first("//ss:sheet[@name='sdrf']") if sheet.nil?
      #sheet = doc.find_first("//ss:sheet[@name='Sdrf']") if sheet.nil?
      #sheet = hunt_for_sheet(doc, "SDRF") if sheet.nil?