What's the criteria to remove docker versions from the archive list?

Currently using “Docker 17.05” . Just noticed that’s it’s not listed in the doc archive list for docker version. What causes a specific docker version to be removed from the list? Is this documented some where?

  • Docker 17.12(current)
  • Docker edge
  • Docker 17.09
  • Docker 17.06
  • Docker 17.03
  • Docker 1.13
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