Table 1. Open access routes.

Open access route	Definition
Gold OA	Articles published in an OA journal, in which all articles are accessible directly and freely on the journal or publisher website, and which does charge publication fees 11, 17.
Platinum OA	Articles published in an OA journal, in which all articles are accessible directly and freely on the journal or publisher website, and which does not charge publication fees to the author since costs are met by one or more sponsoring organizations 21.
Green OA	Articles published in a subscription journal, but self-archived by other parties than the publisher, usually the authors themselves, in open repositories. Open repositories can be disciplinary or institutional repositories and articles may be either accepted versions or electronic preprints 7, 11, 17.
Hybrid OA	Articles published in a subscription journal but that are immediately free to read under an open license, in exchange for APCs paid by the author(s) 11, 22.
Delayed OA	Articles published in a subscription journal but that are free to read after an embargo period 22.
Bronze OA	Articles free to read on the journal or publisher website, but without a clearly identifiable license 11, 19.