On the the page http://www.treebase.org/treebase-web/home.html, which describes the features of treebase, there is a string which reads:
"Data are delivered in several serializations, including NEXUS and NeXML"
It appears that the link for "NEXUS" is broken. When clicked, the link takes you to this page: http://www.treebase.org/hackathon.nescent.org/Supporting_NEXUS_Documentation, which says: "Sorry, page not found. You may continue your search here".
Perhaps the link should direct here (http://informatics.nescent.org/wiki/Supporting_NEXUS), instead?