In a strong reference the ReferenceMaker's implementation of ReferenceMaker::IsRealDependency() returns TRUE. The strong direct reference represents an ownership relationship. Ownership can be shared when multiple reference makers make strong references to a single reference target.
The existence of a strong reference to a reference target prevents the deletion of the target object by 3ds Max. When the last strong reference to a target is removed then the target is automatically deleted. The exception to this are nodes - a strong reference to a node does not prevent that node from being deleted by the user.
If a strong reference to a target exists, then the target is serialized (loaded or saved) whenever the reference maker is serialized.
Parameter blocks ( IParamBlock2 ) that store parameters for a plug-in must be owned by the plug-in. Therefore a strong reference must be made from the plug-in to the parameter block. Note however that plug-ins should use weak references to observer parameter blocks owned by other plug-ins.