“…, n, as a multivariate nonstationary process. The problem of modeling nonstationary processes has been studied in the literature by means of spectral representations (Priestley (1965), Dahlhaus (1996Dahlhaus ( , 1997), pseudo-differential operators (Mallat, Papanicolaou, and Zhang (1998)), discrete non-decimated wavelets (Nason, von Sachs, and Kroisandt (2000)) and smooth localized complex exponentials (Ombao, von Sachs, and Guo (2005)). Other contributions can be found in Cheng and Tong (1998), Giurcanu and Spokoiny (2004), and Draghicescu, Guillas, and Wu (2009), among others.…”