Syma Helicopters Official Site
You can read many detail and information about Syma Helicopters in their manufacturer site. Detail like complete features, technical specification and etc.
http://www.symatoys.com/

Syma Helicopters on Wikipedia
In this wikipedia, you can browse the complete list of Syma helicopter toys products including Syma Helicopters.
http://en.wikipedia.org/wiki/Radio-controlled_helicopter