Hypertex version of asthelp:
http://www.sr.bham.ac.uk/asterix
ROSAT news items:
http://ledas-www.star.le.ac.uk/rosat-goc.html
http://heasarc.gsfc.nasa.gov/
http://www.sr/bham.ac.uk/asterix
LEDAS user guide:
http://ledas-www.star.le.ac.uk/rosat-goc/doc.html
Calibration report:
ftp://legacy.gsfc.nasa.gov/rosat/doc/hri/hri_report