Bip39 ozon https://hubpages.com/@lefwenuuyr Even though it employs BIP32 approach you can continue to import BIP39 seeds into Electrum wallet. Also besides BIp32 there is BIP44 Variation which some wallet use to the technology of seeds. For words that have only three letters, there is absolutely no 4th letter. One example https://ez-bookmarking.com/story20548666/bip39-bip44-compatible-software-wallet-the-5-second-trick-for-bip39-mnemonic-code-converter-tool-https-t-me-bip39-chat