The 
                  noteref element represents a textual reference to a 
                  
                     note (block)
                     .
                  
               
               Note references typically appear as superscripted numbers or symbols within the narrative flow but may also appear as linked
                  words, especially in electronic formats.
               
               The 
                  
                     ref
                      attribute is used to establish the link between the note reference and its associated 
                  note.
                  
               
               By default, the text content of the 
                  noteref represents the link reference and is treated as document content. When superscripted numbers or symbols are used to identify
                  the corresponding 
                  note, the 
                  
                     value
                      attribute should be used. The 
                  noteref must be an empty element when attaching a 
                  value attribute; it it not permitted to include text content and a 
                  value attribute.
                  
               
               Usage details available in the Usage Details section.
               
             
            Usage Example
<p>THE following pages contain Extracts from LETTERS addressed 
    to Professor HENSLOW<noteref ref="n2" value="2" /> by C. DARWIN, Esq. … </p>
…  
<note xml:id="n2">
    <p>John Stevens Henslow (1796-1861), Cambridge clergyman, botanist and mineralogist. 
        He became Darwin's scientific mentor when at Cambridge and received and 
        preserved Darwin's Beagle specimens during the voyage.</p> 
</note>
    Allowed parents
            address, 
               annoref, 
               annotation (block variant), 
               annotation (phrase variant), 
               m:annotation-xml, 
               aside (block variant), 
               aside (toc variant), 
               block, 
               caption, 
               citation (block variant), 
               citation (phrase variant), 
               d, 
               definition, 
               description (block variant), 
               description (phrase variant), 
               emph, 
               entry (toc variant), 
               entry (index variant), 
               entry (bibliography variant), 
               entry (glossary variant), 
               expansion, 
               xforms:group, 
               h, 
               hd, 
               hpart, 
               item, 
               xforms:label, 
               ln, 
               d:longdesc, 
               meta, 
               note (block variant), 
               note (phrase variant), 
               noteref, 
               object (block variant), 
               object (phrase variant), 
               sel:otherwise, 
               p, 
               ssml:phoneme, 
               ssml:prosody, 
               quote (block variant), 
               quote (phrase variant), 
               its:rb, 
               ref, 
               xforms:repeat, 
               its:rt, 
               s, 
               ssml:say-as (phrase variant), 
               ssml:say-as (text variant), 
               d:simplifiedLanguageDescription, 
               span, 
               spine, 
               ssml:sub, 
               d:summary, 
               td, 
               term, 
               th, 
               d:tour and 
               sel:when
               
            
            Allowed children
            This element may contain text.
            
            This element may contain the following children: abbr, 
               address, 
               annoref, 
               ssml:break, 
               char, 
               code, 
               d, 
               definition, 
               emph (text variant), 
               emph (phrase variant), 
               expansion, 
               xforms:input, 
               rend:linebreak, 
               ln, 
               m:math, 
               name, 
               note, 
               noteref, 
               num, 
               object (text variant), 
               object (phrase variant), 
               pagebreak, 
               ssml:phoneme (text variant), 
               ssml:phoneme (phrase variant), 
               ssml:prosody (text variant), 
               ssml:prosody (phrase variant), 
               xforms:range, 
               ref, 
               its:ruby, 
               s, 
               ssml:say-as (text variant), 
               ssml:say-as (phrase variant), 
               xforms:secret, 
               sel:select, 
               xforms:select, 
               xforms:select1, 
               span (phrase variant), 
               span (text variant), 
               sub, 
               ssml:sub (text variant), 
               ssml:sub (phrase variant), 
               sup, 
               term, 
               xforms:textarea, 
               time, 
               ssml:token (text variant), 
               ssml:token (phrase variant) and 
               w
               
            
            Content model and additional requirements
            
               required attributes: 
@ref
                  
                
               optional attributes: 
@about, 
                  
@by, 
                  
@class, 
                  
@content, 
                  
@continuation, 
                  
@datatype, 
                  
@desc, 
                  
@its:dir, 
                  
@its:translate, 
                  
@property, 
                  
@rel, 
                  
@resource, 
                  
@rev, 
                  
@role, 
                  
@sel:selid, 
                  
@ssml:onlangfailure, 
                  
@typeof, 
                  
@value, 
                  
@xml:base, 
                  
@xml:id, 
                  
@xml:lang and 
                  
@xml:space 
               
               a choice of
                  
                  either no content
                  
                  or 
one or more of 
                     
                     a choice of either one of the 50 elements: 
abbr, 
address, 
annoref, 
char, 
code, 
d, 
definition, 
emph, 
emph, 
expansion, 
its:ruby, 
ln, 
m:math, 
name, 
note, 
noteref, 
num, 
object, 
object, 
pagebreak, 
ref, 
rend:linebreak, 
s, 
sel:select, 
span, 
span, 
ssml:break, 
ssml:break, 
ssml:phoneme, 
ssml:phoneme, 
ssml:prosody, 
ssml:prosody, 
ssml:say-as, 
ssml:say-as, 
ssml:sub, 
ssml:sub, 
ssml:token, 
ssml:token, 
sub, 
sup, 
term, 
time, 
w, 
w, 
xforms:input, 
xforms:range, 
xforms:secret, 
xforms:select, 
xforms:select1 or 
xforms:textarea 
                        or text
end of choice 
                     
                   
                  end of choice 
               Note that in addition to restrictions presented in the content model  above, 
                  					use of this element must also respect the following requirements:
                  
                     - The 
                        
value attribute can only be used on empty 
                        noteref elements.
                        
                      
                     - A 
                        
noteref element cannot be empty and not include a 
                        value attribute.
                        
                      
                     - The IDREF(s) in the 
                        
ref attribute must resolve to 
                        note elements.
                        
                      
                     - Superscripted referents should be included in a 
                        
value attribute, not as text content.
                        
                      
                  
                  Such requirements take precedence over any conflicting statements in the
                     						content model or in the lists above of allowed children and parents.
                  
                
             
            Namespace
            http://www.daisy.org/ns/z3998/authoring/
            Usage Details
            
             There are two means of tagging references to notes. When a superscripted identifier is used, the 
               value attribute is required: 
               
            
            
            
               
<p>THE following pages contain Extracts from LETTERS addressed 
    to Professor HENSLOW<noteref ref="n2" value="2" /> by C. DARWIN, Esq. … </p>
        
                
            
             In the above example, the note identifier (the number 2) is no longer part of the document content, but can still be output
               and repurposed by a processing agent. 
            
            
             It is sometimes the case, however, that using one or more words in the content to link to the annotation is preferred to
               a superscripted identifier. In this case, the 
               value attribute is omitted and the text content of the 
               noteref becomes the linkable text: 
               
            
            
            
               
<p>THE following pages contain Extracts from LETTERS addressed 
    to <noteref ref="n2">Professor HENSLOW</noteref> by C. DARWIN, Esq. … </p>
        
                
            
             An additional benefit to tagging words instead of inserting superscripted referents is that a transformation process could
               automatically remove the link from the words and instead insert superscripted numbers or symbols after the element when they
               are needed. It would not be possible to do the reverse if only the superscripts have been tagged, however. 
            
            
             It is illegal to use an empty element and omit a 
               value attribute, as in the following example, as some text content is necessary to render the link: 
               
            
            
            
               
<p>THE following pages contain Extracts from LETTERS addressed 
    to Professor HENSLOW<noteref ref="n2" /> by C. DARWIN, Esq. … </p>
        
                
            
             It is also illegal to use text content together with a 
               value attribute, as it introduces ambiguity in how to format the output: 
               
            
            
            
               
<p>THE following pages contain Extracts from LETTERS addressed 
    to <noteref ref="n2" value="2">Professor HENSLOW</noteref> by C. DARWIN, Esq. … </p>