def self.disjoint_taxon_name_relationships
    self.parent.disjoint_taxon_name_relationships +
        self.collect_to_s(TaxonNameRelationship::Iczn::Invalidating::Homonym::Primary,
                          TaxonNameRelationship::Iczn::Invalidating::Homonym::Primary::Forgotten) -
        self.collect_to_s(TaxonNameRelationship::Iczn::Validating::UncertainPlacement)