There is the Friedrich and Petrus method, but where is Roux, ZZ, ZB, and the other methods?Daphne456456Minec (talk) 21:21, November 13, 2017 (UTC)
Sorry, I meant that there was no Petrus method here, not Roux method.Daphne456456Minec (talk) 21:22, November 13, 2017 (UTC)