1. ## Subgroup of D4

I'm trying to find all of the subgroups in $D_{4}$ of the order 4.

So far I can only get the subgroup set consist of $R_{0}, R_{90}, R_{180}, R_{270}$

Shouldn't there be two more?

I'm trying to find all of the subgroups in $D_{4}$ of the order 4.
So far I can only get the subgroup set consist of $R_{0}, R_{90}, R_{180}, R_{270}$