@article{CRMATH_2014__352_2_137_0,
     author = {Guan, Qi'an and Zhou, Xiangyu},
     title = {An $ {L}^{2}$ extension theorem with optimal estimate},
     journal = {Comptes Rendus. Math\'ematique},
     pages = {137--141},
     publisher = {Elsevier},
     volume = {352},
     number = {2},
     year = {2014},
     doi = {10.1016/j.crma.2013.12.007},
     language = {en},
     url = {http://www.numdam.org/articles/10.1016/j.crma.2013.12.007/}
}