Suggest adding another non standard IVT reference In addition to the alternative proof link non standard calculus possibly add refference to the Constructivist analysis article There is a is a long section on IVT in that page The Constructivist analysis IVT section forward references to this page A link to that discussion might be usefull in this article However I believe the that the the discussion of classical analysis IVT on that page is not in close aggrement with this page 138 162 0 45