How do I write a retraction for "Bob is an Idiot"?

Question

Mike is Bob identical twin brother and was acting like and idiot so an author wrote "Bob is an Idiot."

Days later, it was discoverd that Mike is the fool so the article was wrong. What needs to be done if:

Situation 1: The article was printed (newspaper, flier, etc)

Situation 2: The article was uploaded (blog, web site, etc)

Answer 1

For Situation 1, since it printed and you could have millions of copies, you can print a second article saying the Bob article was wrong and why.

For Situation 2. Just delete it and d the same as above.