reviewed his book
Kościół Chrystusowy w Polsce w latach 1921–1953 (
The Church of Christ in Poland in the Years 1921–1953, 1992), noting that it was based on extensive source material, typically from state archives of former religious and political authorities, describing this as an "extraordinary strength of the historical work". In 2009, Tomaszewski published
Zjednoczony Kościół Ewangeliczny 1947–1987 (
United Evangelical Church 1947–1987). praised it as a valuable resource for novice historians studying evangelical issues in the
Polish People's Republic and those interested in the topic. However, he noted that Tomaszewski portrayed the Office for Religious Affairs as consistently obstructing the United Evangelical Church's operations, even placing Tadeusz Dusik – positively regarded by others – among problematic directors. He also depicted
Szymon Biliński as nearly responsible for the
arrests of United Evangelical Church activists in 1950. Tomaszewski listed 10 agents whose reports the Ministry of Public Security used for the 1950 arrests, though three were recruited after the arrests, and two provided no material. reviewed his 2008 book
Baptyści w Polsce w latach 1918–1958 (
Baptists in Poland in the Years 1918–1958), commending its "wealth of sources" but criticizing its over-reliance on state archives and underuse of Baptist Church archives. He noted scant information on congregational activities, which he considered the essence of the church, while it focused heavily on the Supreme Church Council and its relations with the
Ministry of Religious Affairs and Public Education pre-war and the Office for Religious Affairs post-war. Seweryn also criticized the extensive discussion of tangential issues (e.g., clergy repression in the
Soviet Union, Bulgaria, and
Czechoslovakia, and Office interference with the Christian Ecumenical Council) and noted that chapter summaries were mere restatements lacking synthesis or deep conclusions. considered him one of the most effective authors on religious minorities from 1945 to 1989, but faulted him for superficial archival research and ignoring existing literature. He deemed Tomaszewski's view – that religious authorities were uninterested in dogmatic or organizational matters – far removed from the realities of confessional policy, though he valued him for "other merits". == Selected publications ==