Your own ideas...but make sure they are your own
Your conclusion...if you are restating things you already cited in your paper
Common knowledge...this one is a little trickier, how do you decide if something is common knowledge?
- many scientific and historical facts fall into this category (Lincoln was assassinated, Einstein originated the theory of relativity)
- things you would expect people would already know (the United States is made up of many ethnic groups)
- common sayings, quotes, or folklore ("ask not what your country can do for you, ask what you can do for your country")
If you are not sure, ask your teacher or a librarian!