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git-svn-id: svn://svn.r-forge.r-project.org/svnroot/qca@40 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Added function "retention" (previously "perturb" and created documentation; updated documentation; renamed data sets

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/qca@41 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
no comment

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/qca@42 edb9625f-4e0d-4859-8d74-9fd3b1da38cb