. . . "Definition: A reference from an instance of a class in this ontology to an object in an external resource.\nComment: Instances of the xref class should never be created and more specific classes should be used instead."^^ . "Definition: A reference from an instance of a class in this ontology to an object in an external resource.\nComment: Instances of the xref class should never be created and more specific classes should be used instead."^^ . "Definition: A reference from an instance of a class in this ontology to an object in an external resource.\nComment: Instances of the xref class should never be created and more specific classes should be used instead."^^ . . . . . . . . . . . . .