Documentation for create unique index is insuficient and (because ofthat) incorrect

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/11/static/indexes-unique.html
Description:

In https://www.postgresql.org/docs/11/static/indexes-unique.html there are
omited clausules

For example WHERE clausule is omited. 

In https://www.postgresql.org/docs/11/static/sql-createindex.html you can
see the right sintax with all the clausules.