Nationalities map of the Province of East Prussia / on the basis of official data made by Paul Langhans. The data on the languages are based on reports of the Royal Prussian Statistical State Office. The municipality units according to their mother tongue on 1 December 1900.
<bdi><a href="https://en.wikipedia.org/wiki/en:Paul_Langhans" class="extiw" title="w:en:Paul Langhans"><span title="German geographer">Paul Langhans</span></a>
</bdi>
1907<div style="display: none;">date QS:P571,+1907-00-00T00:00:00Z/9</div>
<a rel="nofollow" class="external autonumber" href="http://gauss.suub.uni-bremen.de/suub/hist/index.jsp?id=Kt.+I-896">[1]</a>