Decades: 20s BC 10s BC 0s BC 0s 10s - 20s - 30s 40s 50s 60s 70s
Years: 20 21 22 23 24 - 25 - 26 27 28 29 30
Births
Deaths
... \sqrt {b^2-4ac}</math> in the formula should be understood as "either of those element(s) of the field whose square equals b2 - 4ac". In some fields, so ...