Carrick, Michael (2005). "Thunder Gun". Discovering Lewis & Clark (published May 2005). Archived from the original on 2010-06-13. Retrieved 2017-04-28.
Mike Waldren. "Arming the police"., see section "1836 – Protection of Royal Palaces"
postalheritage.org.uk
The British Postal Museum and Archive. "Weapons". Archived from the original on 2008-08-07. Retrieved 2008-07-07.[dead link], see items OB1995.338 and OB1995.344
Carrick, Michael (2005). "Thunder Gun". Discovering Lewis & Clark (published May 2005). Archived from the original on 2010-06-13. Retrieved 2017-04-28.
The British Postal Museum and Archive. "Weapons". Archived from the original on 2008-08-07. Retrieved 2008-07-07.[dead link], see items OB1995.338 and OB1995.344