@calendar indicates the system or calendar to which the date represented by the content of this element belongs, but this element has no textual content. The element should not be categorized in detail with @subtype unless also categorized in general with @type @targetLang can only be used if @target is specified. The element indicated by @spanTo must follow the current element @spanTo on must point to the identifier of some element in this document Only one of the attributes @target and @cRef may be supplied on . Only one of the attributes @target' and @cRef' may be supplied on If the @target attribute on is used, the relatedItem element must be empty A relatedItem element should have either a 'target' attribute or a child element to indicate the related bibliographic item An lg element must contain at least one child l, lg or gap element. You may not nest one s element within another: use seg instead Only one of the attributes @target and @from may be supplied on Only one of the attributes @target and @to may be supplied on If @to is supplied on , @from must be supplied as well The attributes @to and @from on may each contain only a single value On , either the @marks attribute should be used, or a paragraph of description provided A feature value cannot contain both text and element content A feature value can contain only one child element You may not supply both @target and @targets on You must supply either @target or @targets on You must supply at least two values for @target on You may not supply both @target and @targets on You must supply either @target or @targets on You must supply at least two values for @target on You may not supply both @target and @targets on You must supply either @target or @targets on The element may appear once only The element may appear once only The element may appear once only You must supply either a locator of some type or a name for Only one of the attributes @active and @mutual may be supplied the attribute 'passive' may be supplied only if the attribute 'active' is supplied Only one <lem> element may appear within a single apparatus entry, whether it appears outside a <rdgGrp> element or within it. The spanTo= attribute of is required. The @spanTo attribute of is required. The spanTo= attribute of is required. must have at least one child add and at least one child del Child elements of are only allowed when an external module is being loaded The prefix attribute of should not match that of any other element (it would defeat the purpose) On element the value of the module attribute ("") should correspond to an existing module, via a moduleSpec or moduleRef Class : the value of the module attribute ("") should correspond to an existing module, via a moduleSpec or moduleRef Macro : the value of the module attribute ("") should correspond to an existing module, via a moduleSpec or moduleRef Rules in the Schematron 1.* language must be inside a constraint with a value of 'schematron' on the scheme attribute Rules in the ISO Schematron language must be inside a constraint with a value of 'isoschematron' on the scheme attribute Attribute: the definition of the @ attribute in the should have a closed valList or a datatype