@Book{BVMC:789089, author = {Unamuno, Miguel de}, title = {Carta de Miguel de Unamuno a Manuel Ugarte. Oporto, 6 de julio de 1904}, publisher = {Alicante : Biblioteca Virtual Miguel de Cervantes, 2017}, year = {2017}, url = {https://www.cervantesvirtual.com/nd/ark:/59851/bmcpz794} }