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The easiest way to prove you are the author is to post something on your original site (readynutrition.com) where you claim your Steem account. I think we can work with the cheetah bot creators to white list those who do proper verification / linking.

Ready Nutrition republished this from my site - Nutritional Anarchy, with my permission. I added a link to my original source above. Thanks!

I added a link to the original source - my website - for verification. This is my original work and can be found at the link I provided at the end of my article. Thanks!

I would think if you edited the original article on your site and added a blurb at the bottom that you have republished to steemit with link here then that would be sufficient proof that you're the author or at least owner of that site.