'Phags-pa script
Although the "Hunminjeong'eum Haerye" explains the design of the consonantal letters in terms of articulatory phonetics, as a purely innovative creation, several theories suggest which external sources may have inspired or influenced King Sejong's creation. Professor Gari Ledyard of Columbia University studied possible connections between Hangul and the Mongol 'Phags-pa script of the Yuan dynasty. He believed that the role of 'Phags-pa script in the creation of the Korean alphabet was quite limited: