The dependence and independence of quantifiers
truth, proof and choice functions
pp. 49-72
in: Kevin Mulligan, Tomasz Placek (eds), The history and philosophy of Polish logic, Berlin, Springer, 2014Abstract
A function f is continuous at a point x0 if given any ε > 0 one can choose δ > 0 so that for all y, when x0 is within distance δ from y, then f(x0) is within distance ε from f(y).