@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}}
}
