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<!ELEMENT dictionary (entry+)>
<!ELEMENT entry ((definition+, synonym*, antonym*)|(reference))>
<!ATTLIST entry word ID #REQUIRED>
<!ELEMENT definition (#PCDATA)> 
<!ATTLIST definition
	domain (biology|computing) #IMPLIED
>
<!ELEMENT synonym (#PCDATA)>
<!ELEMENT antonym (#PCDATA)>
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   target IDREF #REQUIRED
>