If it's a whole string of articles on that subject chances are it's spam. Flag the hubs for the moderators and they will check them. Also, if it's the same person, check their profile. Have they written anything else useful? Have the recently joined and posted dozens of articles? These kinds of things can indicate a need to flag the persons profile for the HP moderators as well.
Spam is not tolerated on HP, but it takes all of us contributing to make this site the best it can be for all of us.
That being said, some articles on SEO are truly useful and have been written by hubbers truly trying to help other writers. (I'm a guilty party here too lol) However, a whole string of them in a row seems fishy and probably is a spammer, so please take action when you see things like that :)