2.1.372 Part 1 Section 17.14.18, linkToQuery (Query Contains Link to External Query File)
a. The standard says this element specifies that the query string contains a reference to an external query file that contains the actual query data to be used against the specified external data source for the mail merge.
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Word saves this element irrespective of whether the query string actually contains a reference to an external query file or not, and subsequently ignores the element.