Typo in doc.

git-svn-id: http://svn.zoo-project.org/svn/trunk@461 4b6b6ad6-68b3-4dcc-9231-bd9b83bc5dc3
Typo in doc.

git-svn-id: http://svn.zoo-project.org/svn/trunk@462 4b6b6ad6-68b3-4dcc-9231-bd9b83bc5dc3
Typo in doc.

git-svn-id: http://svn.zoo-project.org/svn/trunk@463 4b6b6ad6-68b3-4dcc-9231-bd9b83bc5dc3