From the date, the frontpage (http://www.open-std.org/jtc1/sc22/wg14/www/standards) link to the rationale document points to a newer version: http://www.open-std.org/jtc1/sc22/wg14/www/docs/C99RationaleV5.10.pdf

On Wed, Jun 17, 2020 at 4:41 PM Steve Downey via SG16 <sg16@lists.isocpp.org> wrote:

http://www.open-std.org/jtc1/sc22/wg14/www/docs/n850.pdf

The relevant parts seem to be 5.2.1 Character Sets, and forward.
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