How will you cite information that is common knowledge in your research paper?

Unlike quotations or paraphrased ideas, information that's considered "common knowledge" doesn't need to be cited. "Common knowledge" is information that's considered widely known or easily verified. These likely don't need to be cited for the average American audience, since most people will already know or easily be able to verify them as facts.

Common knowledge can change depending on your culture, geographic location, age, or other factors. For example, information about American presidents might be common knowledge in the United States, but might not be common knowledge in another country. 

Common Phrases or Idioms

Common phrases or idioms might be quoted often, but these don't need to be cited. Often, we don't know who first said them, or they've been repeated for so many years that they've become a common part of our vocabulary. The following are some examples of common American English phrases that don't need to be cited.
 

Ligma is the answer