Czechoslovakia 1930: linguistic
<ul><li>derivative work: <a href="//commons.wikimedia.org/wiki/User:Wimox" title="User:Wimox">Henry Mühlpfordt</a> / <a href="//commons.wikimedia.org/wiki/File:Czechoslovakia_1930_linguistic_map_-_en.jpg" title="File:Czechoslovakia 1930 linguistic map - en.jpg">Czechoslovakia 1930 linguistic map - en.jpg</a>: Mariusz Pazdziora</li></ul>
CC BY 3.0
<ul><li><a href="//commons.wikimedia.org/wiki/File:Czechoslovakia_1930_linguistic_map_-_en.jpg" title="File:Czechoslovakia 1930 linguistic map - en.jpg">Czechoslovakia 1930 linguistic map - en.jpg</a></li></ul>