Second book of Math Contest Books Series:
https: //www.amazon.com/Balls-Boxes-Yongcheng-Chen/dp/1540390578
Third book of Math Contest Books Series:
https: //www.amazon.com/dp/1540856410
Second book of Math Contest Books Series:
https: //www.amazon.com/Balls-Boxes-Yongcheng-Chen/dp/1540390578
Third book of Math Contest Books Series:
https: //www.amazon.com/dp/1540856410
Paperback
$19.91