\begin{thebibliography}{10}

\frenchspacing

\bibitem{bisker1}
J. Bi\v{s}ker, \emph{On the elements
of the empty set}. Mathematica Absurdica
\textbf{132} (1999), 13--113.

\bibitem{pyrl}
U. P\^{y}r{\l}\aa, \emph{Generalization
of Bi\v{s}ker's theorem}. Paperopolis
J. Math. \textbf{14} (2001), 125--132.

\end{thebibliography}
