中国科学院数学与系统科学研究院期刊网
A Characterization of L(2,1)-Labeling Number for Trees with Maximum Degree 3
Dong CHEN, Wai Chee SHIU, Qiao Jun SHU, Pak Kiu SUN, Wei Fan WANG
Acta Mathematica Sinica, Chinese Series . 2016, (5): 685 -710 .  DOI: 10.12386/A2016sxxb0062