MIB import of a single MIB file fails with message:
The MIB referenced by the selected file appears to contain more than one MIB definition. Each MIB definition needs to be in a separate file.
The reference to the external MIB within the imported MIB file is made via "OBJECT-IDENTITY FROM MIB;".
The referenced MIB file exists as a MIB in the MIB Tools Database but not as single MIB file in MIB import directory.