Is REVTeX 4.0 still available?
REVTeX 4.0 may still be needed for legacy documents. Most REVTeX 4 documents should run under REVTeX 4.1 as well. Many TeX distributions remove older packages, so you may need to install REVTeX 4 yourself. It can be downloaded a zip file from http://authors.aps.org/revtex4/4/revtex4.zip. REVTeX 4 and REVTeX 4.1 can be installed side-by-side on the same computer without interfering each other. New documents should be created using REVTeX 4.1, especially if you are planning on submitting to an APS journal.