Who wrote the eight words on the gate of Nanjing University?

Mao Zedong. The gate of hankou road Old Campus of Nanjing University is located at the south entrance of Beiyuan, which is open to the atmosphere. The whole gate is in the shape of a "door", and two thick square columns support the door head, on which are written the four glittering Chinese characters "Nanjing University". On the right side of the column, eight characters of "unity and tension" and "seriousness and liveliness" are embossed. This is Mao Zedong's inscription for NTU's teaching policy as early as April 1937.