https://pubmed.ncbi.nlm.nih.gov/?term=advance+directives[mh]+OR+((advance+directive*[tw]+OR+living+will*[tw])+NOT+Medline[sb])+AND+English[la]+AND+(systematic[sb]+OR+((clinical[tiab]+AND+trial[tiab])+OR+clinical+trial[pt]+OR+random*[tiab]+OR+random+allocation[mh]+OR+therapeutic+use[sh]))