code: @Override
      public ReferencesBuilder append(final String reference, final int section) {
          return doAppend(Collections.singletonList(new Reference(reference, section)));
      }
docs: Appends the specified reference and section number to this instance, returning {@code this}.
  
  @param reference The reference to append
  @param section The section number of the reference to append
  @return {@code this}