Diseases unwritten in medical books.
出自: N. HawthorneThe unwritten law that priests and journalists have a right to protect their sources.
出自: A. MacVicarConforming to this unwritten and indeed unspoken rule.
出自: A. Brookner"an unwritten law"
"rites...so ancient that they well might have had their unwritten origins in Aurignacian times"
"an oral tradition"
"an oral agreement"
"he made a few ad-lib remarks"