Ooms, M., Koopman, S. and Carnero, A. (2007). Periodic Seasonal Reg-ARFIMA-GARCH Models for Daily Electricity Spot Prices Journal of the American Statistical Association, 102(477):16--27.
Menkveld, A., Koopman, S. and Lucas, A. (2007). Modelling Round-the-Clock Price Discovery for Cross-Listed Stocks using State Space Methods Journal of Business and Economic Statistics, 25(2):213--255.