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Description: A doubleton word is a word. (Contributed by Stefan O'Rear, 23-Aug-2015) (Revised by Mario Carneiro, 26-Feb-2016)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | s2cl |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | simpl | ||
| 2 | simpr | ||
| 3 | 1 2 | s2cld |