| Metamath Proof Explorer |
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Related theorems Unicode version |
| Description: Extend class notation to include the proper substitution of a class for a set into another class. |
| Ref | Expression |
|---|---|
| vx |
|
| cA |
|
| cB |
|
| Ref | Expression |
|---|---|
| csb |
|
| Colors of variables: wff set class |