Source : Webster's Revised Unabridged Dictionary (1913)

Incontrovertible \In*con`tro*ver"ti*ble\, a.
   Not controvertible; too clear or certain to admit of dispute;
   indisputable. --Sir T. Browne. --
   {In*con`tro*ver"ti*ble*ness}, n. -- {In*con`tro*ver"ti*bly},
   adv.

Source : WordNet®

incontrovertibly
     adv : in an obvious and provable manner; "his documentary sources
           are demonstrably wrong" [syn: {demonstrably}, {provably}]