@article{10_4064_ap108_2_1,
     author = {R\'emi Langevin and Jun O'Hara and Shigehiro Sakata},
     title = {Application of spaces of subspheres to
 conformal invariants of curves and canal surfaces},
     journal = {Annales Polonici Mathematici},
     pages = {109--131},
     publisher = {mathdoc},
     volume = {108},
     number = {2},
     year = {2013},
     doi = {10.4064/ap108-2-1},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap108-2-1/}
}