@article{10_4064_ap96_1_5,
     author = {N. S. Hoang and A. G. Ramm},
     title = {Symmetry problems 2},
     journal = {Annales Polonici Mathematici},
     pages = {61--64},
     publisher = {mathdoc},
     volume = {96},
     number = {1},
     year = {2009},
     doi = {10.4064/ap96-1-5},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap96-1-5/}
}