Bip39 one https://www.bitsdujour.com/profiles/wWbptt Regardless that it uses BIP32 technique you are able to still import BIP39 seeds into Electrum wallet. Also other than BIp32 There's BIP44 version which some wallet use for the era of seeds. For words that have only three letters, there isn't any 4th letter. For instance https://funny-lists.com/story21920277/bip39-browser-bip39-compatible-wallet-an-overview-https-linktr-ee-bip39