Referencias: http://factsanddetails.com/world/cat56/sub363/item1526.html https://en.wikipedia.org/wiki/History_of_writing https://www.khanacademy.org/partner-content/big-history-project/agriculture-civilization/first-cities-states/a/uruk http://www.historiaantigua.es/articulos/uruk/uruk.html https://www.historiaeweb.com/2015/04/24/escritura-cuneiforme/