code: public void getReferencingStrongLinks(CmsObject cms, CmsResource resource, Set<String> referencingPaths)
      throws CmsException {
  
          CmsRelationFilter filter = CmsRelationFilter.SOURCES.filterType(CmsRelationType.JSP_STRONG);
          Iterator<CmsRelation> it = cms.getRelationsForResource(resource, filter).iterator();
          while (it.hasNext()) {
              CmsRelation relation = it.next();
              try {
                  CmsResource source = relation.getSource(cms, CmsResourceFilter.DEFAULT);
                  // check if file was already included
                  if (referencingPaths.contains(source.getRootPath())) {
                      // no need to include this file more than once
                      continue;
                  }
                  referencingPaths.add(source.getRootPath());
                  getReferencingStrongLinks(cms, source, referencingPaths);
              } catch (CmsException e) {
                  if (LOG.isErrorEnabled()) {
                      LOG.error(e.getLocalizedMessage(), e);
                  }
              }
          }
      }
docs: Returns a set of root paths of files that are including the given resource using the 'link.strong' macro.<p>
  
  @param cms the current cms context
  @param resource the resource to check
  @param referencingPaths the set of already referencing paths, also return parameter
  
  @throws CmsException if something goes wrong