2.1.683 Part 4 Section 188.8.131.52, sheetView (Chart Sheet View)
a. The standard states that extLst is a child element of sheetView.
In Office, extList is persisted under the parent element, sheetViews. If Office opens a file where sheetViews contains an extLst element, it will persist two extLst elements in sheetViews, making the file invalid.
This note applies to the following products: 2007, 2007 SP1, 2007 SP2.