Hassi Seppo; de Snoo H. S. V.; Szafranieć Franciszek Hugon: Normal intermediate extensions of symmetric relations. In: Acta scientiarum mathematicarum, (80) 1-2. pp. 195-232. (2014)
Larson David R.; Szafranieć Franciszek Hugon: Framings and dilations. In: Acta scientiarum mathematicarum, (79) 3-4. pp. 529-543. (2013)
Szafranieć Franciszek Hugon: The Sz.-Nagy "théorème principal" extended. Application to subnormality. In: Acta scientiarum mathematicarum, (57) 1-4. pp. 249-262. (1993)
Stochel Jan; Szafranieć Franciszek Hugon: On normal extensions of unbounded operators II. In: Acta scientiarum mathematicarum, (53) 1-2. pp. 153-177. (1989)