1.  Now, we not only study the new text, but also go over the old knowledge.

2.  We must prepare the new knowledge and go over the old knowledge in this winter holiday.

3.  We can derive from practice everyday, firstly, we can't forget the old knowledge .

4.  Only when you know the old knowledge can you learn the new knowledge.

5.  Some people say that some university degrees present too old knowledges This often happens that education legs behind the development of science, such as physics, chemistry and biology.