protected function convert_assessments_to_links($assessments) {
        $authorlinks    = array(); // [authorid]    => array(reviewerid, reviewerid, ...)
        $reviewerlinks  = array(); // [reviewerid]  => array(authorid, authorid, ...)
        foreach ($assessments as $assessment) {
            if (!isset($authorlinks[$assessment->authorid])) {
                $authorlinks[$assessment->authorid] = array();
            }
            if (!isset($reviewerlinks[$assessment->reviewerid])) {
                $reviewerlinks[$assessment->reviewerid] = array();
            }
            $authorlinks[$assessment->authorid][]   = $assessment->reviewerid;
            $reviewerlinks[$assessment->reviewerid][] = $assessment->authorid;
            }
        return array($authorlinks, $reviewerlinks);
    }