 \begin{equation}
     \begin{split}
         U_{Z_{1-12}} \sim \mathcal{N}(0,1),  \\
         Z_{1-3} := U_{Z_{1-3}}, \; \; Z_{7,9,12}:= U_{Z_{7,9,12}}, \; \; Z_4 := 0.1Z_3 + U_{Z_4}, \; \; Z_5 := -0.2Z_2 + U_{Z_5},\\
         Z_6 := -0.3Z_5+ U_{Z_6}, \; \; Z_8 = 0.5Z_7 + U_{Z_8}, \; \; Z_{10} = 0.4Z_9 + U_{Z_{10}}, \; \;\\
         Z_{11} := 0.5Z_{10} + U_{Z_{11}}.
     \end{split}
 \end{equation}
