Mancini G, Musina R. Surfaces of minimal area enclosing a given body in  R\\\\sp 3. Ann. Scuola Norm. Sup. Pisa Cl. Sci. (4)  16  (1989),  no. 3, 331--354 (1990). [Internet]. 1989  . Available from: http://hdl.handle.net/1963/619