Answer: authoritative

AnswerCrossword Clue
authoritativehaving or proceeding from authority
authoritativeCommanding and self-confident; likely to be respected and obeyed
authoritativeProceeding from an official source and requiring compliance or obedience
authoritativeAble to be trusted as being accurate or true; reliable
authoritative(of a text) Considered to be the best of its kind and unlikely to be improved upon