5442H8 --> http://books.google.es/books?id=72GCAHBl6kIC&pg=PA321&lpg=PA321&dq=construcci%C3%B3n+tunel+atocha+chamart%C3%ADn+1967&source=bl&ots=FY8s7cx9SQ&sig=-pa_b2sI356QbUUTPlu_ZdmefQ0&hl=ca&sa=X&ei=rOHHU7--Nqi70QXHs4G4Aw&ved=0CEQQ6AEwBg#v=onepage&q=construcci%C3%B