We used the Zoho Notebook with a sheet page, we had data and someone did a sort which moved some data out of place then their IE crashed. Thus they could not UNDO to fix their mistaken sort. Is there any way to REVERT to an earlier version of a sheet? I have manually fixed my sheet but would like to know my options if this happens again. What are backup options (I hear there are some if you're not on FREE, what's the $ for NOTEBOOK + SHEET?). Thank you.