Sentence examples similar to not obligatory until from inspiring English sources

Separation of production lines was not obligatory up until 1999 (Table 4), and both producers A and K have used mixed production lines up until then.

But the historical context was not obligatory in the curriculum.

But they are not obligatory for other tournaments, only recommended.

Religious exercises wrere given, but it was not obligatory for any boy to attend.

But I think that kindness is not obligatory in the same sense.

This is however not obligatory for the maximum score.

This is not obligatory, except in clinical trials.

It's not obligatory".

Music is not obligatory.

Rubbing noses is not obligatory.

Bookings are recommended but not obligatory.