I imagine he did it at this very blackboard because, as I said, he had his office in this building and he didn't die until 1940s, so he must have been-- this building was--this room goes back to the '30s.

我猜他就是在这块黑板上解释这个理论的,当时他的办公室就在这栋楼里,他是在40年代离世的,所以他应该曾经...,而这间教室是在30年代建成的

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