Description: A proper subclass does not include the other class. (Contributed by Glauco Siliprandi, 26-Jun-2021)
Ref | Expression | ||
---|---|---|---|
Hypothesis | pssnssi.1 | ||
Assertion | pssnssi |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | pssnssi.1 | ||
2 | dfpss3 | ||
3 | 1 2 | mpbi | |
4 | 3 | simpri |