In recent years it has been strengthening academic and scientific communication in electronic format. This has involved both the proliferation of electronic versions of academic and professional conference proceedings, reports, etc., as the publication of resources originating directly in electronic format magazines. Also, some time ago that some publishers have started to market digital versions of monographs, there are numerous Web resources are for informational and reference value and digitization projects abound in all kinds of texts. Libraries have been integrated in different media collections of information and representing them in catalogs, and so is also happening with the resources electrónicos.Este book is intended as a guide for the selection and cataloging of these resources. At its core, dedicated to cataloging isbd of the texts, in particular the ISBD (ER) and ISBD (CR), and supplemented by the Anglo-American cataloging rules and those concretions and implementation guidelines provide solutions that may be useful to the cataloguer. Throughout the manual, the comments to the rules are illustrated with numerous examples coded in the MARC 21 format The book closes with a collection of annotated bibliographic records representing various types of electronic resources.