Factorable and strictly singular operators in a product space Horacio Porta (1971) Studia Mathematica
Factoring unconditionally converging operators Joe Howard (1979) Commentationes Mathematicae Universitatis Carolinae
Fractional powers of non-densely defined operators Celso Martinez, Miguel Sanz (1991) Annali della Scuola Normale Superiore di Pisa - Classe di Scienze
Full Operators on Reflexive Banach Space S. Karanasios (1994) Δελτίο της Ελληνικής Μαθηματικής Εταιρίας