@incollection{PurBot:82,
  publisher = {Babe\c s-Bolyai University},
  title = {Tolerances},
  olume = {Preprint no. 2},
  author = {Purdea, Ioan and Both, Nicolae},
  year = 1982,
  pages = {8--38},
  series = {Faculty of Mathematics Research Seminaries},
}