We are discussing subtilities when Alan Barret gave already the
citation that is explicit :

----quote
There is no special quoting mechanism for header text. The header text
is the rest of the argument. If multiple header changes are needed,
multiple -o options can be used, such as:

ps -o "user=User Name" -o pid=Process\ ID
----endquote
-- 
Thierry Laronde (Alceste) <tlaronde +AT+ polynum +dot+ com>
                 http://www.kergis.com/
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