Volume and Quantizations
  The aim of this letter is to indicate the differences between the Rovelli-Smolin quantum volume operator and other quantum volume operators existing in the literature. The formulas for the operators are written in a unifying notation of the graph projective framework. It is clarified whose results apply to which operators and why. 
Jerzy Lewandowski (Institute of Theoretical Physics, Warsaw University   and Max-Planck-Institut f\"ur Gravitationsphysik, P...