Bip39 Seed To Mnemonic. From this issue ahead the seed might be published on paper or spoken above phone and this opened up new, physical ways of backing up the seed (multiple paper copies in several places, strong copies on metal plates with more safety from fireplace/flood and so on.). https://socialtechnet.com/story4081194/seed-phrase-words-list-how-much-you-need-to-expect-you-ll-pay-for-a-good-bip32-vs-bip39