The guidance on contained resources has contradictory guidance on references to contained resources.

The bullet point

• A contained resource SHALL only be included in a resource if something in that resource (potentially another contained resource) has a reference to it.

and the sentence

Resources can only be contained in other resources if there is a reference from the resource to the contained resource, or if the contained resource references the container resource. This is intended to ensure that the meaning of the contained resource is clear, and that there is no confusion as to its significance.

differ, one has an "or".

This is normative