Christoph Burnikel Stefan Funke Kurt Mehlhorn Stefan Schirra Susanne Schmitt A Separation Bound for Real Algebraic Expressions. 14-28 2009 55 Algorithmica 1 http://dx.doi.org/10.1007/s00453-007-9132-4 db/journals/algorithmica/algorithmica55.html#BurnikelFMSS09