1. $\exists x N(x)$
Some student has visited North Dakota
2. $\forall x N(x)$
All students have visited North Dakota
3. $\neg \ \exists x N(x)$
No student has visited North Dakota
4. $ \exists x \neg N(x)$
Some student has not visited North Dakota
5. $\sim \forall x N(x)$
Not all students have visited North Dakota
6. $\forall x \sim N(x)$
All students have not visited North Dakota