@article{TM_2007_258_a3,
     author = {F. Aicardi and V. A. Timorin},
     title = {On {Binary} {Quadratic} {Forms} with the {Semigroup} {Property}},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {28--48},
     publisher = {mathdoc},
     volume = {258},
     year = {2007},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TM_2007_258_a3/}
}