From the following http://www.msnbc.msn.com/id/8633818/
So the question is have you ever used something other than paper for your books?
LIMA, Peru - Archaeologists in Peru have found a “quipu” on the site of the oldest city in the Americas, indicating that the device, a sophisticated arrangement of knots and strings used to convey detailed information, was in use thousands of years earlier than previously believed...
So the question is have you ever used something other than paper for your books?