homepages/234/6227,
Vivian Motti and Vivian Genaro Motti, Home Page, https://www.mendeley.com/profiles/vivian-motti/, Catholic University of Louvain, Louvain-la-Neuve, Belgium
homepages/51/3710-119,
Yang Liu, Home Page, https://orcid.org/0000-0002-4304-4519, Dalian University of Technology, School of Mathematical Sciences, Dalian, China
homepages/51/3710-120,
Yang Liu, Home Page, https://orcid.org/0000-0001-7495-282X, Chinese Academy of Sciences, Institute of Geographic Sciences and Natural Resources Research, Beijing, China