Identifier of a journal, book, conference proceedings, or other publication that is (or contains) the target of the <related-object>.
External Identifier: This element holds an external identifier assigned to a publication that is part of the description of a related object (<related-object>). The contents of this attribute should not be confused with the @id attribute, which holds an internal document identifier that can be used by software to preform a simple link.
Used along with @source-id-type to identify the publication that is (or contains) the target of the <related-object> element. The @source-id might contain an ISBN as content, and the @source-id-type should indicate that this identifier is an ISBN.
Best Practice: For each source, document, and object, an identifier is specified on the corresponding attribute. If the source and document are the same, the @source-id attribute should be empty. If the document and object are the same, the @object-id attribute should be empty. The @document-id attribute should always be specified.
... <related-object source-id="http://www.ncbi.nlm.nih.gov/entrez/ query.fcgi?cmd=Retrieve&dopt=Expanded&db=nlmcatalog&list_uids=1252893" source-id-type="url" source-type="book"> <person-group person-group-type="editor"> ...</person-group> <source>Disease and Mortality in Sub-Saharan Africa</source> ...</related-object> ...