Surfaces of minimum capacity for a knot
Annali della Scuola Normale Superiore di Pisa - Classe di Scienze, Serie 4, Volume 2 (1975) no. 4, p. 497-505 
@article{ASNSP_1975_4_2_4_497_0,
     author = {Caffarelli, Luis},
     title = {Surfaces of minimum capacity for a knot},
     journal = {Annali della Scuola Normale Superiore di Pisa - Classe di Scienze},
     publisher = {Scuola normale superiore},
     volume = {Ser. 4, 2},
     number = {4},
     year = {1975},
     pages = {497-505},
     zbl = {0313.31014},
     mrnumber = {393523},
     language = {en},
     url = {http://www.numdam.org/item/ASNSP_1975_4_2_4_497_0}
}

Caffarelli, Luis A. Surfaces of minimum capacity for a knot. Annali della Scuola Normale Superiore di Pisa - Classe di Scienze, Serie 4, Volume 2 (1975) no. 4, pp. 497-505. http://www.numdam.org/item/ASNSP_1975_4_2_4_497_0/

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