http://www.gtoal.com/history.dcs.ed.ac.uk/archive/os/VMS-filestore/
http://www.gtoal.com/history.dcs.ed.ac.uk/archive/os/APM-filestore/FS.1976
http://www.gtoal.com/history.dcs.ed.ac.uk/archive/os/APM-filestore/FS.hier