Radon-Nikodym theorems for nonnegative forms, measures and representable   functionals
  The aim of this note is to establish two Radon--Nikodym type theorems for nonnegative Hermitian forms defined on a real or complex vector space. We apply these results to prove the known Radon--Nikodym theorems of the theory of representable positive functionals, $\sigma$-additive and finitely additive measures. 
Zsigmond Tarcsay
math.FA