Decomposition of unbounded derivations into invariant and approximately inner parts. O. Bratteli; G. A. Elliott; P. E. T. Jorgensen — 1984 Journal für die reine und angewandte Mathematik
Quasianalytic vectors and derivations of operator algebras. O. Bratteli; R. H.,Robinson, D. W. Herman — 1976 Mathematica Scandinavica