@article{10_4153_CMB_1986_005_0,
     author = {Harrington, David J.},
     title = {Co-Rank of a {Composition} {Operator}},
     journal = {Canadian mathematical bulletin},
     pages = {33--36},
     year = {1986},
     volume = {29},
     number = {1},
     doi = {10.4153/CMB-1986-005-0},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1986-005-0/}
}