@article{10_4153_CMB_2010_094_2,
     author = {Bouali, S. and Ech-chad, M.},
     title = {Generalized {D-symmetric} {Operators} {II}},
     journal = {Canadian mathematical bulletin},
     pages = {21--27},
     year = {2011},
     volume = {54},
     number = {1},
     doi = {10.4153/CMB-2010-094-2},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-2010-094-2/}
}