When designing the document, new features of the FB2.1 format were used. In particular, the document has different accessibility depending on the user’s access level (subscriber/outsider). Part of the document is completely hidden from everyone except the owner of the document. For example, documents the publication of which is prohibited by the copyright holder should be drawn up in this way. This format of publications, among other things, is completely legitimate - quoting copyrighted works is legal. Probably, the authors will also not be against this type of publication, since it can contribute to the growth of the popularity of their books. However, this can equally prevent you from peddling some nonsense to your readers. Well... That's what quotation is for, isn't it? Let's try to play fair with each other. Documentation on the new features of fb2.1 is under development.