Yu, Peiqiu; Li, Jinjin; Lin, Guoping: 'Vector-based approaches for computing approximations in multigranulation rough set', The Journal of Engineering, 2018, 2018, (16), p. 1538-1543, DOI: 10.1049/joe.2018.8317
IET Digital Library, https://digital-library.theiet.org/;jsessionid=2e2m6pv5hnvpj.x-iet-live-01content/journals/10.1049/joe.2018.8317