@article{BASS_2005_30_1_a5,
     author = {A. L. Barrenechea and C. C. Pena},
     title = {On derivations over rings of triangular matrices},
     journal = {Bulletin de l'Acad\'emie serbe des sciences. Classe des sciences math\'ematiques et naturelles},
     pages = {77 - 84},
     publisher = {mathdoc},
     volume = {30},
     number = {1},
     year = {2005},
     url = {http://geodesic.mathdoc.fr/item/BASS_2005_30_1_a5/}
}