I'll check.
Maybe that's a good point. We can't think of anything, but if you don't include “orally or in writing”, then it leaves it up to jurisprudence to determine that, if you leave it not specified in the legislation. If you put it in, then it could be limited if somebody does come up with something that couldn't be considered orally or in writing, such as sign language.
We'd have to check on that, but that would be just one of the things to consider.