State the cases where "Doctrine of supervening impossibility" does not apply.

In the following cases contracts are not discharged on the ground of supervening impossibility. Difficulty of performance: The mere fact that performance is more difficult or expensive than the parties anticipated does not discharge the duty to perform. Commercial impossibilities do not discharge the contract. A contract is not discharged merely because expectation of higher profits is not realised. Strikes, lockouts and civil disturbance like riots do not terminate contracts unless there is a clause in the contract providing for non-performance in such cases.