????:1?????????:??????????

2?????????

3????????

4?????vx

5???????????

??2?21?????? (?? ?)2?????????????????????21?????????,????????????????????????,????????????????;?????????????????????

?????,???,1977??????11?,??????????????,?????????

???????????????????,1973?????5???,??,???????????????????????????????????????,??

???,1971?????????2?????????,????????????????????????????????,???(?????????????) ??:??