Utilisateur:CaféBuzz/Brouillon/Goma-2
https://oa.upm.es/47713/9/TESIS_MASTER_GONZALO_F_GARCIA_FERNANDEZ.pdf
http://info.igme.es/SidPDF/065000/089/65089_0001.pdf
https://ocw.unican.es/pluginfile.php/2434/course/section/2465/tema_1.3.pdf
https://www.elcorreo.com/vizcaya/20090314/pvasco-espana/goma-para-reventar-bancos-20090314.html
https://www.elmundo.es/elmundo/2007/06/01/espana/1180724976.html
https://elpais.com/diario/2006/07/16/espana/1153000807_850215.html