On some symmetrical equations of the form f 1 ( x 1 + . . . + x n ) = ∑ i 1 , . . . , i n ) f 1 ( x i 1 ) . . . f n ( x i n ) H. Światak — 1967 Annales Polonici Mathematici
A construction of continuous functions without the usual, the approximative and the distributional derivatives H. Światak — 1965 Annales Polonici Mathematici
On the functional equation f ( x + y - x y ) + f ( x y ) = f ( x ) + f ( y ) H. Swiatak — 1968 Matematički Vesnik