Centro Italiano Studi Vessillologici: http://www.cisv.it/

http://www.rbvex.it/

http://www.vexilla-mundi.com/new.html

World Flag Database: http://www.flags.net/

 http://www.flaginstitute.org/wp/

Flags of the World: http://www.crwflags.com/fotw/flags/

Flaggenlexicon: http://www.flaggenlexikon.de/

http://www.vexillographia.ru/

Vexilologia Brasileira: http://www.vexilologia.com.br/index.html

http://www.netstate.com/states/tables/state_flags.htm

https://www.britannica.com/search?query=flag

http://www.worldstatesmen.org/

https://www.vexilologie.cz/

http://abcounties.com/flags/county-flags-an-introduction/

https://simbolospatrios.net/