Letov Š-20J s motorem Walter Jupiter (1928)
neznámý (unknown)
Letectví, Vol. 8. (1928), No. 6. (June), p. 204f - <a rel="nofollow" class="external free" href="https://kramerius.army.cz/search/i.jsp?pid=uuid:25908a71-51e9-11e9-8c09-005056b73ae5">https://kramerius.army.cz/search/i.jsp?pid=uuid:25908a71-51e9-11e9-8c09-005056b73ae5</a>