An operator inequality. Siafarikas, P.D. — 1984 International Journal of Mathematics and Mathematical Sciences
A singular functional-differential equation. Siafarikas, P.D. — 1982 International Journal of Mathematics and Mathematical Sciences
A counterexample to an assertion due to Blumenthal. Ifantis, E.K.; Siafarikas, P.D. — 2001 Zeszyty Naukowe Uniwersytetu Jagiellońskiego. Universitatis Iagellonicae Acta Mathematica