-lemma isrt_inv_shift: â\88\80n,c. ð\9d\90\91ð\9d\90\93â¦\83n,â\86\95*câ¦\84 â\86\92 ð\9d\90\91ð\9d\90\93â¦\830,câ¦\84 ∧ 0 = n.
+lemma isrt_inv_shift: â\88\80n,c. ð\9d\90\91ð\9d\90\93â\9dªn,â\86\95*câ\9d« â\86\92 ð\9d\90\91ð\9d\90\93â\9dª0,câ\9d« ∧ 0 = n.