public List<SelectItem> getX509SigningReferenceTypeList() {
    List<SelectItem> items = new ArrayList<SelectItem>();

    items.add(
        new SelectItem(
            X509SigningRefType.DIRECT.toInt(), X509SigningRefType.DIRECT.toLocaleString()));
    items.add(
        new SelectItem(
            X509SigningRefType.KEY_IDENTIFIER.toInt(),
            X509SigningRefType.KEY_IDENTIFIER.toLocaleString()));
    items.add(
        new SelectItem(
            X509SigningRefType.ISSUER_SERIAL.toInt(),
            X509SigningRefType.ISSUER_SERIAL.toLocaleString()));

    return items;
  }