中国科学院数学与系统科学研究院期刊网
AMS
The Almost Global and Global Existence for Quasi-linear Wave Equations with Multiple-Propagation Speeds in High Dimensions
Yi DU, Zheng An YAO
Acta Mathematica Sinica . 2011, (6): 1205 -1220 .  DOI: 10.1007/s10114-011-8017-2