@article{MZ_1993__213_1_174532,
     author = {Georgi S. Popov},
     title = {Length spectrum invariants of {Riemannian} manifolds.},
     journal = {Mathematische Zeitschrift},
     pages = {311--352},
     publisher = {mathdoc},
     volume = {213},
     number = {1},
     year = {1993},
     zbl = {0804.53068},
     url = {http://geodesic.mathdoc.fr/item/MZ_1993__213_1_174532/}
}