Given a set $X=\{1,\dots,n\}$. In Dempster–Shafer theory a BBA is a function $m:\mathcal P(X)\to[0,1]$, with the two properties that $m(\emptyset)=0$ and $\sum_{A\subseteq X}m(A)=1$.
The Dempster's rule of combination of two BBAs is defined $(m_1\oplus m_2)(\emptyset)=0$ and
$(m_1\oplus m_2)(A)=\frac{1}{1-K}\sum_{B\cap C=A}m_1(B)m_2(C)$, where
$K=\sum_{B\cap C=\emptyset}m_1(B)m_2(C)$.
My question is if this composition of BBAs is associative. I can't find anything anywhere about that.