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

有時候最難的事情和最正確的事情是同一件事。

The man who is fit to work at any particular trade is unable to understand the science of that trade without the kindly help and cooperation of men of a totally different type of education.

我不是一個喜歡普通的人。

Collaboration is essential in research; no one can solve big problems alone.

數學是諸神與人類交談的語言。