When a parent speaks to a child in a certain tone of voice so that the child knows he must obey, that is an example of an authoritative voice.
A supervisor who is in charge of setting schedules is an example of a person who is authoritative.
The captain's authoritative manner.
An authoritative decree; authoritative sources.
A book written by an expert on certain subject matter is an example of an authoritative book.
The authoritative rules in this school come not from the headmaster but from the aged matron.
An authoritative account of the revolution.
An authoritative biography.