“…Generalizations to multivariate space-time processes have been considered in Alegría, Porcu, Furrer, and Mateu (2019). The richness in modeling stochastic processes over spheres or spheres cross time is reflected in the diversity of research in this area: Mathematical analysis (Barbosa & Menegatto, 2017;Beatson, Zu Castell, & Xu, 2014;Chen, Menegatto, & Sun, 2003;Gangolli, 1967;Guella, Menegatto, & Peron, 2016a, 2016bHannan, 1970;Menegatto, 1994Menegatto, , 1995Menegatto, Oliveira, & Peron, 2006;Schoenberg, 1942), probability theory (Baldi & Marinucci, 2006;Clarke, Alegria, & Porcu, 2018;Hansen, Thorarinsdottir, Ovcharov, & Gneiting, 2015;Lang & Schwab, 2013), spatial point processes (Møller, Nielsen, Porcu, & Rubak, 2018), spatial geostatistics (Christakos & Papanicolaou, 2000;Gerber, Mösinger, & Furrer, 2017;Gneiting, 2002b;Hitczenko & Stein, 2012;Huang, Zhang, & Robeson, 2012), space-time geostatistics (Berg & Porcu, 2017;Christakos, 1991aChristakos, , 2000Christakos, Hristopulos, & Bogaert, 2000;Porcu et al, 2016) and mathematical physics (Istas, 2005;Leonenko & Sakhno, 2012;Malyarenko, 2013).…”