@article{10_2307_121061,
     author = {Barry Simon},
     title = {A new approach to inverse spectral theory. {I:} {Fundamental} formalism},
     journal = {Annals of mathematics},
     year = {1999},
     volume = {150},
     number = {3},
     doi = {10.2307/121061},
     zbl = {0945.34013},
     url = {http://geodesic.mathdoc.fr/articles/10.2307/121061/}
}