In general, books preserve information of enduring relevancy, and newspapers disseminate information of fleeting relevancy. The information provided by newspapers stimulated agitated discussions of concrete events and the merits of contemporary state authorities. Many Europeans migrated to North American to avoid repression by state authorities for their heretical ideas. One of the major issues was how to establish a state structure deemed sufficiently powerful to maintain social order and prevent foreign invasions. Several European nations instituted state structures that were composite palace- and legislature-centered structures and several dictatorships were established. Newspapers and pamphlets were widely used to criticize traditional state structures and advocate democracy. Some totalitarian states tolerate commercial newspapers but maintain close surveillance of them. More recently, social media have displaced both broadcast and print journalism. "Social media technologies like Twitter are part of a range of Internet technologies enabling the disintermediation of news and undermining gatekeeping function of journalists".