Let $A$ be a representation finite hereditary algebra. Define the Euler form by $f(M,N):=dim(Ext^1(M,N))-dim(Hom(M,N))$ for two modules $M,N$. Now if $A_1$ and $A_2$ are two representation-finite hereditary algebra with the same underlying quiver, there is a bijection between the basic tilting modules of these algebras. Is there such a bijection between the tilting modules which preserves the Euler form? I think yes, but I'm not sure why or Im missing a reference.