R. B. Alvarez and J. M. Bravo, "Forecast Combination for Asset Classes ETFs: Insights on Market Efficiency and Arbitrage", in Proc. of 20th Iberian Conf. on Information Systems and Technologies (CISTI 2025). Lecture Notes in Networks and Systems., Rocha, A., García Peñalvo, F., Costa, C.J., Gonçalves, R. , Ed., Springer, Cham, 2026, vol. 1717, pp. 274-286