Extension and exact realization of the Heller's derivative rule
  The accuracy of the Heller's derivative rule to calculate the numerical weights associated with discretized energy spectrum is enhanced by Broad's extension which adds (N-1) more interpolating points to the original N points. The extension scheme is then used to show how to realize the rule without any approximation. 
Hashim A. Yamani, Abdulaziz D. Alhaidari
math-ph math.MP