@article{AFM_1990_15_2_a5,
     author = {R.W. Cross},
     title = {The essential state diagram of a linear operator},
     journal = {Annales Fennici Mathematici},
     pages = {283--291},
     publisher = {mathdoc},
     volume = {15},
     number = {2},
     year = {1990},
     doi = {10.5186/aasfm.1990.1506},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.5186/aasfm.1990.1506/}
}