http://www.amazon.com/Help-Your-Kids-Math-problem/dp/0756649...
http://www.amazon.com/Math-Power-Child-Dover-Mathematics/dp/...
http://www.amazon.com/What-Help-Child-Math-Myself/dp/0974168...
Amazon.co.uk
http://www.amazon.co.uk/Help-Your-Kids-Math-Problem/dp/07566...
http://www.amazon.co.uk/Math-Power-Child-Dover-Mathematics/d...
http://www.amazon.co.uk/What-Help-Child-Math-Myself/dp/09741...
My favourites are the Rob Eastaway / Mike Askew books:
http://www.amazon.com/More-Maths-Mums-Askew-Eastaway/dp/0224...
http://www.amazon.com/Maths-Mums-Dads-Rob-Eastaway-ebook/dp/...
http://www.amazon.co.uk/Maths-Mums-Dads-Mike-Askew/dp/022408...
http://www.amazon.co.uk/More-Maths-Mums-Dads-Askew/dp/022409...
(Amazon: Please have some really easy way to give me a clean url for sharing. I am literally sending potential customers to your website.)
Or the book "Maths for mums and dads" is useful.
https://www.amazon.co.uk/Maths-Mums-Dads-Mike-Askew/dp/02240...
https://www.amazon.co.uk/More-Maths-Mums-Dads-Askew/dp/02240...