This article introduces three other keyword trend tools that Amazon sellers must know.
1. Thesaurus.com :
http://thesaurus.reference.com/
2. Dependency-based Word Similarity :
http://www.cs.ualberta.ca/%7Elindek/demos/depsim.htm
3. Hitwise Search Intelligence :
http://www.hitwise.com/
The above are other keyword trend tools that Amazon sellers must know, I hope it will be helpful to you.