B.11. Future revisions of this license
The Free Software Foundation may publish new, revised
versions of the GNU Free Documentation License from time to time.
Such new versions will be similar in spirit to the present
version, but may differ in detail to address new problems or
concerns. See https://www.gnu.org/copyleft/.
Each version of the License is given a distinguishing
version number. If the Document specifies that a particular
numbered version of this License "or any later version" applies to
it, you have the option of following the terms and conditions
either of that specified version or of any later version that has
been published (not as a draft) by the Free Software Foundation.
If the Document does not specify a version number of this License,
you may choose any version ever published (not as a draft) by the
Free Software Foundation.