@article{10_4153_CJM_1973_016_6,
     author = {Sussmann, H\'ector J.},
     title = {Generalized {Spectral} {Theory} and {Second} {Order} {Ordinary} {Differential} {Operators}},
     journal = {Canadian journal of mathematics},
     pages = {178--193},
     year = {1973},
     volume = {25},
     number = {1},
     doi = {10.4153/CJM-1973-016-6},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1973-016-6/}
}