@inbook {BHI01, title = {Heuristics for the {PNS} problem}, booktitle = {Optimization theory: Recent development from M{\'a}trah{\'a}za}, year = {2001}, pages = {1-18}, author = {Z. Bl{\'a}zsik and Cs. Holl{\'o} and Cs. Imreh and Z. Kov{\'a}cs} }