**4. Conclusion**

The periodic restricted *EXPAR* model is added to the family of nonlinear and periodic models. Interest is focused on estimation and testing problems. The

*The Periodic Restricted EXPAR(1) Model DOI: http://dx.doi.org/10.5772/intechopen.94078*

periodic stationarity allows to calculate the QML estimators and derived tests of coefficients, cycle by cycle, and therefore use standard techniques. From this point of view, we can extend several results concerning the classical *EXPAR* to the periodic case.
