@article{Cegielski:2009,
author
=
"A.Cegielski",
title
=
"A generalization of the Opial's theorem",
journal
=
"Control and Cybernetics",
volume
=
"Vol. 36",
number
=
"no. 3",
pages
=
"601--610",
year
=
"2007",
}