The wikipedia archive from 20120104 is no longer available on the standard download server, so we host it here. S3 limits file size, so it is split it chunks of 5*10**8 bytes. To reassemble it, you can fetch each of these links and then:
cat enwiki-20120104-pages-articles.xml.xz-xa? > enwiki-20120104-pages-articles.xml.xz
xzcat enwiki-20120104-pages-articles.xml.xz