Изменения

=== Разность <texttex>R1 \setminus R2</tex> === R <font color = grey>::</font> R1 <font color = blue>where ¬∃$\lnot\exists$</font>R2 <font color = grey>(</font>R1 <font color = grey>=</font> R2<font color = grey>)</font>