 (00,00)[(0,0)\[c\][[$\widetilde{a}$ or $\widetilde{b}$ or $\widetilde{c}$]{}]{}]{}  (00,0)[(0,0)\[l\][[Fig. 0. Subtree $T_{0}$.]{}]{}]{}  (00,00)  (00,00)[(00,0)\[c\][[($[0.0,0.0],$ $[0.0,0.0])$]{}]{}]{}  (00,00)[(0,-0)[0]{}]{} (00,00)[(0,0)[00]{}]{} (00,00)[(0,-0)[0]{}]{}(00,00)[(0,-0)[0]{}]{}  (00,00)[(00,0)\[c\][[($ [0.0,0.0],$ $[0.0,0.0])$]{}]{}]{} (00,00)[(00,0)\[c\][[($ [0.0,0.0],$ $[0.0,0.0])$]{}]{}]{} (00,00)[(0