@article{10_4153_CMB_2011_074_3,
     author = {Gustafson, Karl},
     title = {On {Operator} {Sum} and {Product} {Adjoints} and {Closures}},
     journal = {Canadian mathematical bulletin},
     pages = {456--463},
     year = {2011},
     volume = {54},
     number = {3},
     doi = {10.4153/CMB-2011-074-3},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-2011-074-3/}
}