“…Therefore, coherently with the classic arbitrage pricing theory the mean returns can be approximated by the linear pricing relation 0 where δ j for j=1,...,k, are the risk premiums relative to the different factors. In particular, when we consider a three-fund separation model which depend on the first three moments, we obtain the so called Security Market Plane (SMP) (see, among others,Ingersoll (1987),Pressacco and Stucchi (2000), and Adcock et al (2005)). However, the approaches (6),(7), and (8) generalize the previous fund separation approach.…”