@article{Kahlig:2009,
author
=
"P.Kahlig and J.Matkowski",
title
=
"Envelopes of special class of one-parameter families of curves",
journal
=
"Demonstratio Mathematica",
volume
=
"Vol. 29",
number
=
"no 4",
pages
=
"799--806",
year
=
"1996",
}