Secrets of Mental Math (Kindle eBook) $2

[chris]

http://amzn.to/2DVugoA
https://play.google.com/store/books/details/Arthur_Benjamin_Secrets_of_Mental_Math?referrer=utm_campaign=asdf&id=ykz7uzPEMjEC

https://www.barnesandnoble.com/w/se...=AFF&SID=NOK_DRS_ProductCatalogNook_20150928&