Complex sentence: Sygnały Magazyn (Signals Magazine), a Polish cultural and social magazine published 1933--1939 in Lwów (Lemberg, today Lviv, Ukraine), was a leading periodical of the leftist Polish intelligentsia.
Split into simpler sentences: Sygnały Magazyn (Signals Magazine) was a Polish cultural and social magazine published 1933--1939 in Lwów (Lemberg, today Lviv, Ukraine). It was a leading periodical of the leftist Polish intelligentsia.