```ruby
cask 'epub-to-pdf' do
  version '3.1'
  sha256 'dcfc59d57f756802e844614b7dae43bca67284ec85fe6b909f244e41f20987b3'

  url "https://storage.googleapis.com/google-code-archive-downloads/v2/code.google.com/epub-2-pdf/e2p-#{version.major}.dmg"
  name 'epub-2-pdf'
  homepage 'https://code.google.com/archive/p/epub-2-pdf'
  license :oss

  app 'epub-to-pdf.app'

  caveats do
    discontinued
  end
end
```

Fix `url` stanza comment for epub-2-pdf.
user
```ruby
cask 'epub-to-pdf' do
  version '3.1'
  sha256 'dcfc59d57f756802e844614b7dae43bca67284ec85fe6b909f244e41f20987b3'

  # googleapis.com/google-code-archive-downloads/v2/code.google.com/epub-2-pdf was verified as official when first introduced to the cask
  url "https://storage.googleapis.com/google-code-archive-downloads/v2/code.google.com/epub-2-pdf/e2p-#{version.major}.dmg"
  name 'epub-2-pdf'
  homepage 'https://code.google.com/archive/p/epub-2-pdf'
  license :oss

  app 'epub-to-pdf.app'

  caveats do
    discontinued
  end
end
```
assistant