@article{10_21136_MB_2000_126275,
     author = {Nebesk\'y, Ladislav},
     title = {A tree as a finite nonempty set with a binary operation},
     journal = {Mathematica Bohemica},
     pages = {455--458},
     publisher = {mathdoc},
     volume = {125},
     number = {4},
     year = {2000},
     doi = {10.21136/MB.2000.126275},
     mrnumber = {1802293},
     zbl = {0963.05032},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/MB.2000.126275/}
}