Terms for subject Scientific containing complexity problem

English	Russian
the complexity of the problem is caused by the fact that	сложность проблемы вызвана тем, что
due to the complexity of the problem it has been necessary to introduce some simplifications	из-за сложности задачи стало необходимо ввести некоторое упрощение
problem of medium complexity	задача средней сложности (Alex_Odeychuk)