He has written on operators of Volterra -type, compact linear operators, the Neumann series of integral operators, algebras of operators, automorphisms and derivations of operator algebras, and the cohomology of operator algebras.
Siya ay nakasulat sa operator ng Volterra-uri, siksik sa guhit operator, ang Neumann serye ng mga mahalaga operator, algebras ng mga operator, automorphisms at derivations ng operator algebras, at ang cohomology ng operator algebras.