2.1.829 Part 4 Section 22.214.171.124, x (Shared Items Index)
a. The standard specifies that the x element is an array of indexes.
Office assumes that the value of x@v is an index into the shared items collection.
b. The standard does not place a limit on the value of @v.
Office requires that @v shall be less than sharedItems count.
c. The standard does not specify different restrictions for @v based on the parent element of x.
In Office if the parent is the reference element, then restrictions of this value are defined by reference@field. If the parent is the tables element, then this value specifies the index into the table tag position in @url.