text: Public domain works are valuable because anyone 
  can freely build upon, enhance, and reuse them for 
  any purposes without restriction under copyright 
  or database law. 
  
  That’s why it’s important for creators to have a clear and 
  legally robust way to place their works in the public domain as 
  completely as possible, and it’s also important for publishers 
  and archives to have a standardized way to identify works that 
  are already in the public domain. 
  
  Creative Commons supports two distinct public domain tools, 
  the CC0 Public Domain Dedication and the Public Domain 
  Mark. Creative Commons copyright licenses help authors 
  manage their copyright on terms they choose. Conversely, CC0 
  enables authors and copyright owners who want to dedicate 
  their works to the worldwide public domain to do so, and PDM 
  facilitates the labeling and discovery of works that are already 
  free of known copyright restrictions. 
  
  Where public domain tools fit in the copyright spectrum 
  
  CC0 
  Public 
  domain 
  Some rights 
  reserved  All rights 
  reserved 
  
  PDM 
  No known 
  copyright 