To index aviation related research the office “Zentralstelle für Wissenschaftliches Berichtswesen der Luftfahrtforschung” (ZWB, engl: Central Office for Scientific Reports in Aeronautical Research) was instigated on November 1, 1933. As there was no official Air Ministry at this time (as Germany was prohibited from having an air force by the Treaty of Versailes in 1919), the ZWB was located at the DVL in Berlin-Adlershof, although it was controlled by the Technical Director of the Air Ministry later. All publishing activity had to be reported to (in many cases also sanctioned by) the ZWB by scientists and engineers researching in the field of aviation, or research fields relevant for aviation (such as meteorology). The ZWB would compile a report listing all publications (the “ZWB-index”). Most of the publications therein were usually technical reports by research institutions, Luftwaffe departments or scientific societies directly sponsored by the Air Ministry (such as the Lilienthal-Society); as universities were controlled by the Ministry of Education, university researchers did not need to report their publications to the ZWB, although occassionally relevant dissertations were added to the ZWB-index. The quality of the reports varies widely, as sometimes only minutes of the meetings of some technical committee was published as technical report.

The text “ZWB-Report” was added by me to distinct them from other reports. The letters and numbers after that are from the original ZWB-index. The letters usually refer to the institution or type of report:

DALDeutsche Akademie für Luftfahrtforschung (Engl: German Academy for Aeronautical Research), founded 1935.
FBForschungsbericht (Engl: Research Report), usually not related to a specific institution, but oftentimes from the DVL, if not specified otherwise on the cover of the report.
JBJahrbuch (Engl: Year Book), usually by the DAL, if not specified otherwise.
LGLilienthal-Gesellschaft für Luftfahrtforschung (Engl: Lilienthal-Society for Aeronautical Research), founded 1936.
PBPrüfbericht (Engl: Test Report), usually not related to a specific institution, but oftentimes from the DVL, if not specified otherwise on the cover of the report.
R.d.L., Ob.d.L.Reichsminister der Luftfahrt, Oberbefehlshaber der Luftwaffe (Engl: Air Secretary, Supreme Commander of the Air Force); title for Hermann Göring, who was both Air Secretary und Supreme Commander of the Luftwaffe (i.e. responsible for both civilian and military aviation). Reports with this signature usually came from either the office of the general surgeon of the Luftwaffe, or from the Aeromedical Research Institute of the Air Ministry.
RechRechlin, i.e. Erprobungsstelle der Luftwaffe Rechlin (Engl: Aeronautical Establishment of the Luftwaffe at Rechlin)
UMUntersuchungen und Mitteilungen (Engl: Investigations and Communications), usually from the DVL, as far as I could make out.
VLFVereinigung für Luftfahrtforschung (Engl: Association for Aeronautical Research), founded 1933.

The ZWB reports on aviation medicine and related topics have been added to the Gaeromed DB.

Source: FIAT Report, Finding Aids in the Archive of the Deutsche Museum