src/HOL/Library/Quadratic_Discriminant.thy
12 months ago nipkow 2018-07-01 added lemmas
2016-07-12 wenzelm 2016-07-12 misc tuning and modernization;
2016-01-05 wenzelm 2016-01-05 updated headers;
2015-06-17 wenzelm 2015-06-17 isabelle update_cartouches;
2015-04-30 paulson 2015-04-30 tidying some messy proofs