Germany philosopher Goethe Zeng Yan: Theory tree of being gloomy, putting into practice is evergreen.

德国哲学家歌德曾言：理论是灰色的，实践之树常绿。

youdao

Germany philosopher Goethe Zeng Yan: Theory tree of being gloomy, putting into practice is evergreen.

德国哲学家歌德曾言：理论是灰色的，实践之树常绿。

youdao