Hi, last week I was about to send a bunch of Chinese books (used, language study books) from Shenzhen to Germany. It was all packed and ready to go until another China Post office worker came up and said, that books can't be send from China, by any means. She explained that it will not go through the customs and will be sent back to me. However, I can't find any information regarding this regulation. Is it possible to send books from China, how?

Thank you.