1. Monotone and convex operator functions;Bendat, Julius;Trans. Amer. Math. Soc.,1955
2. A generalized Schwarz inequality and algebraic invariants for operator algebras;Kadison, Richard V.;Ann. of Math. (2),1952
3. On a representation of additive operator set functions;Neumark, M. A.;C. R. (Doklady) Acad. Sci. URSS (N.S.),1943
4. Positive functions on 𝐶*-algebras;Stinespring, W. Forrest;Proc. Amer. Math. Soc.,1955
5. A moment problem for self-adjoint operators;Sz.-Nagy, Béla;Acta Math. Acad. Sci. Hungar.,1952