2.1.10 External Workbooks

Source relationship: See section 2.1.10.1.

When a package uses an external workbook, it MUST store the location of the workbook using one of the relationships specified in section 2.1.10.1, and that relationship MUST be an explicit relationship from the external link (section 2.1.7.25) part.

An external workbook MUST be located external to the package containing the source relationship (expressed syntactically, the TargetMode attribute of the Relationship element MUST be "External").