- Created by: Todd Whitesides
- Added: 25 Feb 2016
- Find a Grave Memorial 158611885
Find a Grave, database and images (https://www.findagrave.com : accessed ), memorial page for Siemowit Piast of Masovia III (unknown–16 Jun 1381), Find a Grave Memorial no. 158611885, citing Plock Cathedral, Płock, Miasto Płock, Mazowieckie, Poland ; Maintained by Todd Whitesides (contributor 47553735) .