Comets

1) http://nineplanets.org/comets.html

2) http://cometography.com/educate/comintro.html

3) http://www.videojug.com/film/what-is-a-comet

Venus

1) http://nineplanets.org/venus.html

2) http://www.youtube.com/watch?v=HqFVxWfVtoo

3) http://www.accessexcellence.org/WN/SUA09/venus297.php