@post{fedispam,
  author = {Serge Wroclawski},
  year = {2019},
  title = {Preventing spam on the {F}ediverse},
  URL = {https://github.com/emacsen/rwot9-prague/blob/ap-unwanted-messages/topics-and-advance-readings/ap-unwanted-messages.md#postage},
}

@post{hashcash,
  author = {Adam Back},
  title = {Hashcash - A Denial of Service Counter-Measure},
  year = {2002},
}