Hello, I'm trying to select MARC21 tags for our base framework, and I don't know if I'm doing it well: - Internal identifier for this library (ID): 001 - Title: 245.a - Book authors: (No MARC21 tag found) - Legal Deposit Number: 017.a - Copyright/Copyleft specification: 018.a - ISBN: 020.a - ISSN: 022.a - Editor (company): 028.a - Published at Country/City: 044.c - Publication year: 362.a - Time Period of Content/story: 045.b - Place of Content/story: 033.p - Subject of content: 072.a - Source of acquisition: 037.b - Languages of content (of text, audio...): 377.a - Physical description: 007 - Playing time (audio/video): 306.a - Content type (text|audio|video): 336.b - Physical medium (Book|CD|DVD|Tape): 340.e - Digital File Characteristics (format/XviD/MP3/PDF): 347.b - Physical location/shelf in the library: 852.c - Digital Graphic Representation (avatar/cover): 352 (no file?!) - Summary or abstract: 520.a - Genre (lyric/novel/dictionary/jazz): 655.a - Cost in euros: 876.c - Sell price to other libraries: (?) - Public sell price: 365.b - General comments: 500.a - Link to downloadable item (book-PDF/video-AVI/audio-MP3): 774.6 - Link to third-party information: 786.6 - Holding library: 850.a - Pages number: 302.a (obsolete) The purpose is to have a concrete form for cataloguing task of people without any library experience (as me).