@article{AFM_2012_37_1_a10,
     author = {Ferry H. Kwakkel},
     title = {Focal rigidity of hyperbolic surfaces},
     journal = {Annales Fennici Mathematici},
     pages = {149--159},
     year = {2012},
     volume = {37},
     number = {1},
     doi = {10.5186/aasfm.2012.3724},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.5186/aasfm.2012.3724/}
}