Is it permissible to photograph expensive foreign medical references, which are considered the primary source for study, or is it only permissible with the intention of purchasing the original books later?

It is impermissible to photograph or print books whose authors have reserved their copyrights without their permission, because authorship and invention rights are protected by Islamic law. An exception to this is photographing a specific topic or paragraphs for the purpose of benefiting from or citing them, as this does not affect the material or moral rights of the author.