Chinese, Korean, and Japanese all have recognized ways of transcribing their words into the Roman alphabet. In China, the official method is known as Pinyin. Pinyin uses the same characters as does English, with no accents or diacritical marks. Both Korean and Japanese, however, have a couple of marked vowels that occur in transcriptions in these pages. In the book, these are correctly presented, using a special font constructed for the purpose. But the fonts normally available or used in Web browsers do not have the necessary accents, so these pages compromise by using generally available characters.
In romanized Korean, the vowels "o" and "u" may have a "breve" mark over them--an arc open upward. We transcribe these vowels as "oe" and "ue" in most cases. If, however, a word seems likely to be familiar to a Western readership in unaccented form, we omit the trailing "e". In particular, the Korean alphabetic syllabary ought to be written as "Han'guel", but we use "Han'gul" because of its possible familiarity in unaccented form.
Similar considerations apply to romanized Japanese. A long "o" or "u" is properly transcribed with a short bar over it. We double the vowel instead. Hence, the writing of a Japanese word in the Roman alphabet is called "Roomaji." But words that may be familiar are written without the doubling, as in "Hokkaido" rather than "Hokkaidoo."