@Override
  public PortletURL getURLViewDiffs(
      LiferayPortletRequest liferayPortletRequest, LiferayPortletResponse liferayPortletResponse)
      throws Exception {

    PortletURL portletURL =
        liferayPortletResponse.createLiferayPortletURL(
            getControlPanelPlid(liferayPortletRequest),
            PortletKeys.JOURNAL,
            PortletRequest.RENDER_PHASE);

    JournalArticle previousApprovedArticle =
        JournalArticleLocalServiceUtil.getPreviousApprovedArticle(_article);

    if (previousApprovedArticle.getVersion() == _article.getVersion()) {
      return null;
    }

    portletURL.setParameter("struts_action", "/journal/compare_versions");
    portletURL.setParameter("groupId", String.valueOf(_article.getGroupId()));
    portletURL.setParameter("articleId", _article.getArticleId());
    portletURL.setParameter("sourceVersion", String.valueOf(previousApprovedArticle.getVersion()));
    portletURL.setParameter("targetVersion", String.valueOf(_article.getVersion()));

    return portletURL;
  }