@incollection{BroRud:83,
  volume = {33},
  title = {Recurrent covers and {B}oolean equations},
  year = {1983},
  booktitle = {Contributions to lattice theory (Szeged, 1980)},
  pages = {55--86},
  publisher = {North-Holland},
  address = {Amsterdam},
  author = {Brown, Frank Markham and Rudeanu, Sergiu},
  series = {Colloq. Math. Soc. J\'anos Bolyai},
}