色多多在线观看播放-色多多在线观看高清免费-色多多在线观看视频-色多多在线看-欧美aaaaa性bbbbb小妇-欧美aaaav免费大片

To be aware of the idea of social structure and to use it with sensibility is to be capable of tracing such linkages among a great variety of milieux.

The world is what it is; men who are nothing, who allow themselves to become nothing, have no place in it.

合作是科學的關鍵——沒有任何突破是孤立發生的。

數學研究是所有智力和精神進步不可或缺的基礎。