The digitized texts and pictures of the Open Digital Library are of free use for investigation and didactic purposes, mentioning the source from where they were obtained. For commercial or editorial uses of any kind, those interested must request authorization from the institution that owns the work.

Every effort has been made to contact the authors, editors, publishing houses etc. concerning the copyright in order to obtain their permission for online publication. Should there be any cases which have not been considered, we kindly ask to contact us.