From the Wikipedia page 
Polish Historical Society (Polish: Polskie Towarzystwo Historyczne, PTH) is a Polish scientific society for historians. Founded in 1886 in Lwów by Ksawery Liske as a local society, in 1926 it became the Poland-wide organization dedicated to advancing the knowledge and studies in history of Poland. Since 1974 it organizes tournaments of historical knowledge and since 1980 it organizes an academic conference in five year intervals. It has 40 local chapters and over 3,000 members. Since 2005 it has a status of a Public Benefit Organization in Polish law.