From the series the order parameter was conjectured to have the simple form ⟨ ⟨ σ σ n ⟩ ⟩ = ( 1 − − k ′ 2 ) β β , β β = n ( N − − n ) / 2 N 2 . It took many years to prove this conjecture, as the usual corner transfer matrix technique could not be used, because of the higher genus curve. This conjecture was proven by Baxter in 2005 using functional equations and the "broken rapidity line" technique of Jimbo et al. assuming two mild analyticity conditions of the type commonly used in the field of Yang–Baxter integrable models. Most recently, in a series of papers an algebraic (Ising-like) way of obtaining the order parameter has been given, giving more insight into the algebraic structure.