@article{10_21136_MB_2009_140674,
     author = {Bullen, P. S.},
     title = {Accentuate the negative},
     journal = {Mathematica Bohemica},
     pages = {427--446},
     publisher = {mathdoc},
     volume = {134},
     number = {4},
     year = {2009},
     doi = {10.21136/MB.2009.140674},
     mrnumber = {2597237},
     zbl = {1212.26041},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/MB.2009.140674/}
}