Recent studies produced by historians Christian Booß and Helmut Müller-Enbergs also show domestic surveillance in East Germany went far beyond the Stasi's network of IMs. The two work at the BStU and not long ago, they happened across Stasi informant groups into which hardly any research has been conducted. They found that institutions in which people provided information about others were categorized as POZW -- which stood for "Partner in Political-Operative Cooperation." In contrast to IMs feeding information to the Stasi, these people were not forced to sign a document obliging them to pass along information. But they did so nonetheless. Numerous POZW reports are still in existence -- from banks, for example, or libraries, hospitals, registration offices and judiciary agencies.