@article{MO_2003_2_a6,
     author = {A. Ruinskii},
     title = {Kassini {Curve} and an {Equilateral} {Hyperbola}},
     journal = {Matemati\v{c}eskoe obrazovanie},
     pages = {80--88},
     year = {2003},
     number = {2},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MO_2003_2_a6/}
}