Constant Content

From reading the forum, I thought that I learned we are able to submit content published elsewhere as long as it is clear that we are the author. I then submitted one article from my helium account that was accepted immediately. A second article from my helium account was rejected for not being original. Both articles are sitting at helium with my name clearly as the author and I am not aware of any duplicate content out there. (Maybe my article was used on another site and therefore no longer appeared original?)

Are we allowed to take our helium articles that we believe are worthy and submit them to CC for usage rights only?

Copyscape the article and see if someone stole it from Helium. Could be the reason.