 = a_0^{k_{00}}$. For every such a bracket $b \in B_i$, we include $b'$ into $B'_i$.  (-00,-0) arc (0:000:0); (-00,-0) - (-00,-0); (-00,-0) -(-00,-0); (-00.0,-0.0) -(-00.0,-0.0); (-00.0,-.0) - (-00.0,-.0); (-00.00,-0.0) - (-00.00,-0.0