union UnionGuidelineCoverPageNavigationItemGuidelineDocumentGroupNavigationItemGuidelineDocumentLibraryNavigationItemGuidelineDocumentLinkNavigationItemGuidelineDocumentNavigationItem = GuidelineCoverPageNavigationItem | GuidelineDocumentGroupNavigationItem | GuidelineDocumentLibraryNavigationItem | GuidelineDocumentLinkNavigationItem | GuidelineDocumentNavigationItem