Bip39 tool github http://www.mediafire.com/file/uilrjfajg2ami24/pdf-14673-57158.pdf Checksum creation: A checksum is created from this entropy working with SHA-256 hashing, which helps confirm the mnemonic's integrity later. For words that only have 3 letters, there isn't any 4th letter. One example is Together with the word “include”, there aren't any far more letters https://ledbookmark.com/story6363285/bip39-api-top-latest-five-bip39-word-list-pdf-urban-news-https-linktr-ee-bip39