could not copyright it and publish without substantial revision. He was finally convinced to do so by the first director of the National Academy of the Korean Language, Lee Ki-Moon, and the book was published in Korea in 1998. He has also published on Korean cartography, the alliance between Korea and China during the first Japanese invasions, and the relationship between the wars of the Three Kingdoms and the founding of the Japanese state from Korea. He also wrote a book about the journal written by the 17th century Dutch explorer Hendrick Hamel who was held hostage in Korea for 13 years. The title of this book is 'The Dutch come to Korea' and was first published in 1971. He was invited to visit North Korea in 1988. Research on the origin of hangul Ledyard believes, following, French orientalist, Jean-Pierre Abel-Rémusat in 1820, that the basic hangul consonants were adopted from the Mongolian Phagspa script of the Yuan dynasty, known as the 蒙古篆字 měnggǔ zhuānzì (Mongol seal script). Only five letters were adopted from Phagspa, with most of the rest of the consonants created by featural derivation from these, as described in the account in the Hunmin Jeong-eum Haerye. However, which letters the basic consonants were differs between the two accounts. Whereas the Haerye implies that the graphically simplest letters ㄱㄴㅁㅅㅇ are basic, with others derived from them by the addition of strokes (though with ㆁㄹㅿ set apart), Ledyard believes the five phonologically simplest letters ㄱㄷㄹㅂㅈ, which were basic in Chinese phonology, were also basic to hangul, with strokes either added or subtracted to derive the other letters. It was these five core letters which were taken from the Phagspa script, and ultimately derive from the Tibetan letters ག ད ལ བ ས. Thus they may be cognate with Greek Γ Δ Λ Β and the letters C/G D L B of the Latin alphabet. (The history of the S sounds between Tibetan and Greek is more difficult to reconstruct.) A sixth basic letter, ㅇ, was an invention, as in the Haerye account. The creation of the vowel letters is essentially the same in the two accounts. Consonantal design The Hunmin Jeong-eum credits the 古篆字 "Gu Seal Script" as being the source King Sejong or his ministers used to create hangul. This has traditionally been interpreted as the Old Seal Script, and has confused philologists because hangul bears no functional