NASA
Nasa Space Science Data Archive: Giotto Mission
This site from the National Space Science Data Center provides information on the Giotto mission which was designed to study Comet P/Halley. The spacecraft encountered Halley on March 13, 1986 and approached to within 600 km. This page...
National Earth Science Teachers Association
Windows to the Universe: Halley's Comet
Fact piece about Halley's Comet.