It is a pseudonymous, collective or posthumous work and 50 years have passed since the date of its publication
It is a photographic work or a work of applied art and 25 years have passed since the year of its creation
It is an audiovisual work or a work made in the course of the author's employment and 50 years have passed since the year of its publication (or creation, whatever date is the latest)
It is another kind of work, and 50 years have passed since the year of death of the author (or last-surviving author)