Gold, green, and black open access - Björk - 2017 - Learned Publishing - Wiley Online Library

"Key points   The debate about open access has until now focused on the gold (journals) versus the green route (manuscript self‐archival). Recently an even more disruptive form of OA has emerged, in the form of illegal article copies retrievable from academic social networks or pirate sites. Illegal, or “black open access”, provides access to a large part of the pay‐walled article output which cannot be found in repositories...."