@article{CMH_1980__55_139837,
     author = {Ruishi Kuwabara},
     title = {On the characterizations of flat metrics by the spectrum.},
     journal = {Commentarii mathematici Helvetici},
     pages = {427--444},
     publisher = {mathdoc},
     volume = {55},
     year = {1980},
     zbl = {0448.58027},
     url = {http://geodesic.mathdoc.fr/item/CMH_1980__55_139837/}
}