Did someone managed to complete bonus objective (evacuate 75% of survivors) in mission 10 "Evacuation"?
Or hidden bonus objective in mission 12 "Fulda gap"?
For Fulda Gap, there is artillery to destroy for 3 points (If you follow the roads towards golf to meet up with the american soldiers and then go on you will encounter it on the field to the right of the road leading towards bravo. It will start firing towards a village, not sure if this is considered a secret or not).
Another extra objective that will give 2 stars is to refuel a couple of helicopters standing halfway to delta from the starting sector, you will meet them if you follow the road towards the delta entrance point where you hook up with the germans.