Chinese Children's Picture Books during Mao's era

I am always interested in children literature. Recently I have focused on the children's picture books that were written and printed during Mao's rule in China. After months searching and reading, I found two libraries that house over 120 Chinese children's picture book that published between 1949 to 1976:

(1) Library of Congress has 133 items which were calssified as "cage materials". It means that you cannot request via ILL;

(2) Princeton University libraries houses mover than 186 Chinese children's books that printed when Mao was in power.

I am assuming that libraries in major research university in CHina and Hong Kong might have a larger collection. That would be a good research project during my next term break.