update

git-svn-id: https://svn.r-project.org/R/trunk@66871 00db46b3-68df-0310-9c12-caf00c1e9a41
add xref

git-svn-id: https://svn.r-project.org/R/trunk@66872 00db46b3-68df-0310-9c12-caf00c1e9a41
update

git-svn-id: https://svn.r-project.org/R/trunk@66874 00db46b3-68df-0310-9c12-caf00c1e9a41