System for Information on Grey Literature in Europe

The "System for Information on Grey Literature in Europe" (SIGLE) was established in 1980, two years after a seminar on grey literature organised by the European Commission in York, England. Operated by a network of national information or document supply centres active in collecting and promoting grey literature, SIGLE was an online, pan-European electronic bibliographic database and document delivery system.

Source: Wikipedia — System for Information on Grey Literature in Europe (CC BY-SA 4.0)