For CD-ROM publishing, observe the ISO 9660 Inter-change Level 1
conventions, which are a subset of the MS-DOS filenaming convention. To
make filenames consistent with ISO standards, use only the uppercase letters
A through Z, the digits 0 through 9, plus the underscore and period characters.
Note: In UNIX, cross-document links to files with mixed-case file names
such as Report.PDF may not work. To avoid this problem, use only uppercase
letters or digits.