The <a href="https://en.wikipedia.org/wiki/en:Bartel_BM-4" class="extiw" title="w:en:Bartel BM-4">Bartel BM-4</a> was a Polish trainer aircraft.
<span lang="en">Anonymous</span><span style="display:none">Unknown author</span>
Letec magazine, volume V, issue 8, page 429, August 1929