Basically a second alphabetical correspondence series, but the ordering is looser and at some point (at Michigan State?) it was labeled a subject series, primarily because it contains substantial groups of files by subject. It contains correspondence filed by correspondent, interfiled subject files containing drafts of essays, notes, pamphlets and photocopies, and correspondence grouped by subject. Many of the subject files repeat material also to be found in Series 4 (Written Works) and 5 (Design Works). Ephemera unaccompanied by correspondence have been removed to Series 8.