Bibliographical references Bell, W. R. and Hillmer, S. C. (1983) "Modeling Time Series with Calendar Variation". J.A.S.A., 78, nº 383. Cleveland, W. S. and Devlin, S. J. (1980) "Calendar Effects in Monthly Time Series: Detection by Spectrum Analysis and Graphical Methods". J.A.S.A., 75, nº 371. Cleveland, W. S. and Devlin, S. J. (1982) "Calendar Effects in Monthly Time Series: Modeling and Adjustment". J.A.S.A., 77, nº 379. Cleveland, W. S. and Grupe, M. R. (1983) "Modeling Time Series when Calendar Effects are presento". Applied Time Series Analysis of Economic Data. A. Zellner (editor). Bureau of the Census. Granger, C. W. J. (1963) "The Effect of Varying Month-Length on the Analysis of Economic Time Series". L'Industria. Milano. Liu, Lon-Mu (1986) "Identification of Time Series Models in the Presence of Calendar Variation". International Journal of Forcasting, 2. Oller, L. E. (1978) Time Series Analysis of Finnish Foreing Trade. Finnish Statistical Society. Pfeffermann, D. and Fisher, J. M. (1982) Festival and Working Days Prior Adjustments in Economic Time Series. International Statistical Review, 50. Stram, D. O. and Wei, W. W. S. (1986) Temporal Aggregation in the Arima Process". Journal of the Time Series Analysis, 7, nº 4. Weiss, A. A. (1984) Systematic Sampling and Temporal Aggregation in Time Series Models. Journal of Econometrics, 26.