Vector fields generating more than one flow. Dorosiewicz, Slawomir; Napiórkowski, Kazimierz — 1995 International Journal of Mathematics and Mathematical Sciences
On generalized eigenfunctions of operators in a Hilbert space Kazimierz Napiórkowski — 1973 Studia Mathematica
Continuous tensor products of Hilbert spaces and product operators Kazimierz Napiórkowski — 1971 Studia Mathematica