With respect to linkages and networks, the evolution of shared classifications of habit has been likened to growing common fingertips. Chances are the classification implicit in the links to sources below is not shared by anybody, which of course does not immediately render it unscientific. Parts of it echo McLuhan’s idea that the medium is the message: letters, diaries, big-character posters, and standardized forms, for example, each get their own separate domain. Other parts of it bring together links to disparate sources that share less in terms of form than with respect to content: denunciations and self-criticisms, to name but two. And yet other parts of it merely centre on specific events of importance on which there happen to be sources that warrant more attention then they have so far received from historians.