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    global $language;
    $translations = translation_path_get_translations("node/42");
    /*
    Returns the paths of all translations of a node, based on its Drupal path:
    array(2) {
        ["de"]=>string(7) "node/42"
        ["en"]=>string(7) "node/43"
    }
    */
    print l(t('Link Title'), $translations[$language->language]); //l() will return the alias to node/42