Related to local volatility are the lattice-based implied-binomial and -trinomial trees — essentially a discretization of the approach — which are similarly used for pricing; these are built on state-prices recovered from the surface. Edgeworth binomial trees allow for a specified (i.e. non-Gaussian) skew and kurtosis in the spot price; priced here, options with differing strikes will return differing implied volatilities, and the tree can be calibrated to the smile as required.[41] Similarly purposed closed-form models have also been developed.