When Must I Cite vs. What is Common Knowledge?

Do you have to cite a source for these terms or this kind of knowledge?

1)  Sigmund Freud invented the terms "id," "ego," and "superego" to describe parts of the human mind.

2)  Einstein invented the equation E=MC².

3)  Euclid invented Π to represent the indeterminate decimal number correlating the radius of a circle to its circumference.

4)  College students carry too much credit card debt. 

5)  College students carried an average of about $500 in credit card debt in 2002.

6)  College students are much less likely to drink to intoxication when drinks cost more.