Seal of the Grand Duke of Lithuania <a href="https://en.wikipedia.org/wiki/Vytautas" class="extiw" title="w:Vytautas">Vytautas the Great</a>.
Unknown author<span style="display: none;">Unknown author</span>
Piekosiński F. Pieczęcie polskie wieków średnich. Cz. 1, Doba piastowska. — Kraków, 1899. S. 282.