Demonstrators in China have recently begun to hold blank pieces of paper at protests. While the paper might say nothing, protesters are sending a clear message, according to Dave Clark, an expert in global protest movements and professor of political science at Binghamton University, State University of New York. The pieces of paper are a metaphor for government censorship.

"In effect, they're saying something without saying anything," said Clark, who runs a project tracking global protests called the Mass Mobilization Project.

The white-paper protests have taken place in multiple cities across China, a phenomenon that is likely to get the ruling Communist Party’s attention, said Clark.

"That sort of solidarity is the kind of thing that's likely to put the government on alert," Clark said. "Perhaps even more than the protests themselves are."