deb [signed-by=/usr/share/keyrings/fe-deb2-archive-keyring.gpg] http://www.math.kobe-u.ac.jp/deb2/ unstable/
deb [signed-by=/usr/share/keyrings/fe-deb2-archive-keyring.gpg] http://www.math.kobe-u.ac.jp/deb2/ mathlibre2020/