Изменения

$A_1$, ..., $A_n$, $B_1$, ..., $B_m$, $C_1$, ..., $C_l$ <font color=blue>where </font> $R_1$<font color=red>{</font>$A_i$ = $A_i$, $B_j$ = $B_j$<font color=red>}</font> ∧ $R_2$<font color=red>{</font>$C_k$ = $C_k$, $B_j$ = $B_j$<font color=red>}</font>