CZ:Ref:DOI:10.1371/journal.pone.0011273

Björk BC, Welling P, Laakso M, Majlender P, Hedlund T, Gudnason G (2010). "Open access to the scientific journal literature: situation 2009". PLoS One 5 (6): e11273. DOI:10.1371/journal.pone.0011273. PMID 20585653. PMC PMC2890572. Research Blogging. ^[e]

For a sample of 1837 randomly chosen scientific articles published in 2008, the availability via Green Open Access or Gold Open Access was found to be about 20% in total in autumn 2009, with significant variations across disciplines.