@article {Hollo03, title = {A partial enumeration algorithm for solving {PNS} problems}, journal = {Mathematical and Computer Modelling}, volume = {38}, number = {7-9}, year = {2003}, pages = {855-864}, author = {Cs. Holl{\'o}} } @article {Hollo02, title = {A Procedure Based on Automaton Theory Approach for Solving Modified PNS Problems}, journal = {Pure Mathematics and Applications}, volume = {13}, number = {1-2}, year = {2002}, pages = {159-169}, author = {Cs. Holl{\'o}} }