This is your introduction. You could change it to your own words. You could also decide to use more than three sources (or less than three!).
There is no doubt that the British, American and Soviet media spent a lot of time and energy telling their people how well the allies were co-operating during World War 2. However, this Case Study has shown me some evidence which puts a question mark over this image of friendly co-operation. Three pieces of evidence have made a strong impression on me.