canon_title_name =
  (#exact-symbol "title")

canon_title =
  (#variadic [canon_title_name] canon_text)

canon_formal_item_name =
  (#exact-symbol "formal-item")

canon_formal_item =
  (#choice [
    (#variadic [canon_formal_item_name canon_title] canon_inline)
    (#variadic [canon_formal_item_name canon_title canon_id] canon_inline)
    (#variadic [canon_formal_item_name canon_title canon_id canon_type] canon_inline)
    (#variadic [canon_formal_item_name canon_title canon_type canon_id] canon_inline)
    (#variadic [canon_formal_item_name canon_title canon_type] canon_inline)
  ])
