Encyclopedia

Wikipedia
Encyclopedia of Astronomy and Astrophysics
Encyclopedias & Dictionaries
Encyclopedia.Com
"Krugosvet"
Different Encyclopaedias (in particularly Boljshaja Sovetskaja)
Encyclopaedia for children "Awanta+"
Britannica Encyclopaedia
BIMA Glossary
Glossary of Space Science Terms
Imagine the Universe! Dictionary A-D
Exploratorium Exhibit Cross Reference - Exhibit
Exploratorium Exhibit Cross Reference - Phenomena Index