Here's a free to use text content analysis tool to quickly check your articles.
Most usefully it displays a tag cloud showing the frequency of words used, this gives you a fast indication whether you are over-doing your use of keywords, or whether you should add more:
Text Content Analyser - UsingEnglish.com
"It's easier to fool people than to convince them that they have been fooled. -- Mark Twain
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Aristopik