@techreport{kam992,
 author = {K. Junosza-Szaniawski and P. Rzążewski},
 title = {On the Complexity of Exact Algorithm for $L(2,1)$-labeling of Graphs},
 institution = {KAM-DIMATIA Series},
 year = {2010},
 number = {992},
 type = {prepublication}
}