UMLR — UML2: Need clarification on circle plus notation for containment

Section 7.3.37, Notation indicates that "The members of the package may be shown within the large rectangle. Members may also be shown by branching lines to member elements, drawn outside the package. A plus sign within a circle is drawn at the end attached to the namespace (package). ". It is unclear if this is intended to apply to any Element owner/ownedElement relationship (such as nested classes, owned behaviors, etc.) or only to packages. Some vendors do support circle-plus notation to depict metamodel containment, others don't. If it applies only to packages, then what is the notation for these other membership associations?