| 1 | 11. L: Sequent List 12. s L.( (s) = 0) 13. s L.|= s  |= < [x1; x2/ M @ N],concl > 14. a:Assignment. s L.a | s  a | < [x1; x2/ M @ N],concl > L:Sequent List.
s L.( (s) = 0)
& ( s L.|= s  |= < M @ (x1  x2.N),concl > )
& ( a:Assignment. s L.a | s  a | < M @ (x1  x2.N),concl > ) |