[Feit–Thompson theorem][1] states that every finite group of odd order is solvable. 

Its proof is near 300 pages so it is definitely not an easy paper to read without a prior knowledge about the general methods that are used in the proof and a fairly detailed sketch of the proof strategy in the hand. 

> What are examples of good expository papers for this theorem?     


  [1]: https://en.wikipedia.org/wiki/Feit%E2%80%93Thompson_theorem