I was reading Robinson's book "A Course in the Theory of Groups". In section 9.1 (Hall $\pi$-subgroups) it is commented that, in an insoluble group, the Hall $\pi$-subgroups may not be conjugate. As an example, the author says that the simple group $PSL(2, 11)$ has subgroups isomorphic with $D_{12}$ and $A_{4}$, which are non isomorphic Hall {2, 3}-subgroups and therefore not conjugates.
I would like to know why $PSL(2, 11)$ has subgroups isomorphic with $D_{12}$ and $A_{4}$.
I never heard before of the subgroup $PSL$, so I tried reading about it a bit. I found the following link: Subgroups of order $12$ of $PSL(2,11)$, which points to "Section II.8 of Huppert's Endliche Gruppen I" book. Unfortunately, I don't know German, so it did not help me.
EDIT: by following the link suggested as an answer (Reference for the subgroup structure of $PSL(2,q)$), I found Suzuki's Group Theory(I) book. In the section 3.6 the author find all the subgroups of $PSL(2, q)$. Problem solved, thanks.