Croatia has no laws against historical revisionism or Holocaust denial. This can be attributed to the change of political system, and the change in the entire system of values as the country became independent. Revisionism was not frowned upon because priority was placed on the re-evaluation of history as recorded during the Communist era, which was therefore deemed almost implicitly tainted, because it systematically omitted or misrepresented issues related to what was perceived to be Croatian nationalism. On the other hand, the revision of history books often went too far in making them increasingly focused on Croatian national issues, even with far-right interpretations of various World War II events. The re-examination of the number of victims of the Independent State of Croatia, particularly the Jasenovac concentration camp and Genocide of Serbs, was fairly common, as well as fairly controversial. Statistical research such as that by Vladimir Žerjavić indicated serious flaws with Yugoslav data, whose sources had been kept secret until 1989.