In accordance with the Copyright Act a work made public may be quoted, in accordance with proper usage to the extent necessary for the purpose. Proper usage means here that the quotation is used in a suitable manner, in aid of one's own creative work and for example to illustrate an issue. The author's name and the source must be indicated to the extent and in a manner required by proper usage.
The copyright owner has the exclusive right to control a work by reproducing it and by making it available to the public. If a researcher has signed a publishing agreement wherein all rights to the article are transferred to the publisher, the publisher or the journal in question may forbid parallel publishing in an open access repository.
Copyrighted material may not be used without permission. Such material are for example different kinds of pictures, drawings, maps and photographs.