@article{10_4153_CMB_1971_079_7,
     author = {Malik, M. A.},
     title = {Some {Remarks} on {Abstract} {Differential} {Operators}},
     journal = {Canadian mathematical bulletin},
     pages = {445--447},
     year = {1971},
     volume = {14},
     number = {3},
     doi = {10.4153/CMB-1971-079-7},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1971-079-7/}
}