alter table docs

[Rob Sargent]

I was just looking up alter table add constraint syntax under 
"current(10)" and we get

        ADD /table_constraint/ [ NOT VALID ]
        ADD /table_constraint_using_index/
There is a description below for the using_index version but none for 
the plain version.  There is a block for the plain version on the CREATE 
TABLE page. Should it not also appear in the ALTER TABLE page?