@online{xkcd,
  author = {Randall Munroe},
  title = {Blue Eyes --- A Logic Puzzle},
  url = {https://xkcd.com/blue_eyes.html},
  urldate = {2021-01-26}
}

@book{fagin1995,
  title = {Reasoning About Knowledge},
  language = {eng},
  publisher = {MIT Press},
  year = {1995},
  isbn = {0262061627},
  author = {Fagin, R. and Halpern, J.Y. and Moses, Y. and Vardi, M.Y.}
}