roman.witula@polsl.pl
konrad.kaczmarek@polsl.pl
edyta.hetmaniok@polsl.pl
damian.slota@polsl.pl
© 2013 Roman Wituła, Konrad Kaczmarek, Edyta Hetmaniok, Damian Słota, published by Slovak Academy of Sciences, Mathematical InstituteThis work is licensed under the Creative Commons License.