Functional differentiation under simultaneous conservation constraints   (Constrained functional differentiation in statistical physics and   hydrodynamics)
  Analytical formulae for functional differentiation under simultaneous K-conservation constraints, with K the integral of some function of the functional variable, are derived, making the proper account for the simultaneous conservation of normalization and statistical averages, e.g., possible in functional differentiation in nonvariationally built physical theories, which gets particular relevance for nonequilibrium, time-dependent theories. 
Tamas Gal