Open Access refers to open accessibility of research publications. Open Access publications can be freely read, copied, printed and linked online by everyone without any charge. This means that their accessibility is not limited to, for example, people that have paid the subscription fee. Open Access publishing is done through open access e-journals or as parallel publications in publication archives. Publishers offer various methods of publishing an open access publication, and the methods differ with regard to whether a charge is applied or not. For example, with regard to Gold Open Access journals, the author pays an article processing charge, which makes the article accessible to all right away. By allowing parallel publishing (Green Open Access), the publisher gives the author a permission to publish a certain version of the article through an open publication archive of the organisation, but often only after a certain embargo period.