-PRODUCTION' &&
          parent.id &&
          parent.id[0] !== '_' &&
          parent.firstElementChild === el
        ) {
          // return the LHS non-terminal element
          return { element: el, id: parent.id };
        }
        return null;
      } else if (
        el.nodeName.match(/EMU-(?!CLAUSE|XREF|ANNEX|INTRO)|DFN/) &&
        el.id &&
        el.id[0] !== '_'
      ) {
        if (
          el.nodeName === 'EMU-FIGURE' ||
          el.nodeName === 'EMU-TABLE' ||
          el.nodeName 