Interstellar Medium
- 1
- Interstellar Medium Learning pages
- Page http://www-ssg.sr.unh.edu/ism/
- About ISM from history of observation to current status of understanding.
- 2
- ARVAL Catalog of Bright Planetary Nebulas
- Page http://www.oarval.org/PNeb.htm
- A text table, with name, size, magnitude, area, NGC number, type, RA, dec., and visual quality.