@article{GT_2009_13_4_a5,
     author = {Ol{\textquoteright}shanskii, Alexander Yu and Osin, Denis V and Sapir, Mark V},
     title = {Lacunary hyperbolic groups},
     journal = {Geometry & topology},
     pages = {2051--2140},
     publisher = {mathdoc},
     volume = {13},
     number = {4},
     year = {2009},
     doi = {10.2140/gt.2009.13.2051},
     url = {http://geodesic.mathdoc.fr/articles/10.2140/gt.2009.13.2051/}
}