Quizá quiso decir: Materials ; 227. Aquilafuente ; 227. Aquilafuente ; 227. Materials ; 227. Graduate Texts in Mathematics, 0072-5285 ; 227 IFIP International Federation for Information Processing, 1571-5736 ; 227 Operator Theory: Advances and Applications ; 227 Advances in Intelligent Systems and Computing, 2194-5357 ; 227 Springer Tracts in Modern Physics, 0081-3869 ; 227 Studies in Fuzziness and Soft Computing, 1434-9922 ; 227 Studies in Computational Intelligence, 1860-949X ; 227 Advances in Polymer Science, 0065-3195 ; 227 Communications in Computer and Information Science, 1865-0929 ; 227 Lecture Notes in Electrical Engineering, 1876-1100 ; 227 La ciencia para todos ; 227 Textos docentes ; 227. Cursos e Congresos ; 227. Documento de trabajo ; 227. Cursos e Congresos ; 227. Documento de trabajo ; 227.