Simplify the following text for a Grade 15 native English-speaking person.
Original: He became a regular member of Warszawskiego Towarzystwa Naukowego ( loosely translated , Warsaw Association of Sciences ) , worked with publications such as the Universal Weekly , Meander , Creation , and renewed his activities as chairman of the Polish PEN Club .
Simplified: He became a regular member of Warszawskiego Towarzystwa Naukowego ( Warsaw Association of Sciences ) , worked with publications such as the Universal Weekly , Meander , Creation , and renewed his activities as chairman of the Polish PEN Club .