Good morningI ve built a BDT model using interest rate and volatility. For that I use three different books: Haug (Options Pricing Formulas) , London (Modelling derivative in C++), Clewlow and Strickland (Implementing Derivatives Models).Base on that i ve got three different results for the same input data. So firs of all view i would like to get your view on which is acdording to you the best.Also I have a concern concerning the two last methods. To price a European Bond Option you know that C(0,0) = sum Q(nt,j) Max (0,P(nt,j) -k) where C(i,J) represents the value o a conting claim at node (i,j) , P(i,j) = the value of the s-maturity bond at node (i,j) , Q(i,j) is the value. at time 0, of a security that pays 1 if node(i,j) is reach 0 otherwise.My concern is relative to Q. In a 2 dimensions you calculate Qup and Qdown. For instance you will have for a 3y period: Qu[3,3],Qu[1,3],Qu[-1,3] and Qd[1,3],Qd[-1,3],Qd[-3,3]If i refer to Clewlow and Strickla example p 244, if have respectively : 0.2242,0.4500,0.2258 and 0.2278,0.4570,0.2293. As you notice Qu[-1,3] and Qd[-1,3] are not the same and this is my concern i don t understand why.If you are using the Haug method i believe you ve got the same Qd and Qu.Then the problem in the Bond otion pricing is to calculate Q(i,j) . i assume Q(1,3) = 0.5*(Qu(1,3) + Qd(1,3) do you think i am right ? All the books show the Bond Option pricing with a yield only so they did not mention that problemThanks a lotI can provide result if needed obvioulsy