There is a Chinese saying 十年磨一劍 (Taking ten years to sharpen a sword.), it has been almost 20 years since I published the first math contest workbook in 2002 This workbook is one-of-a-kind and world's first, I believe. In the past 20 years, I created many workbooks and the reason simply is because I could not find suitable teaching materials to use at my own after-school learning centre. Why I created another workbook...