How to earn double without adding any cost in six months or even shorter time? This is the theme of this book. The author uses the four strategies of ""ensuring cash flow, adding income, cutting expenses and better choices"" to help several enterprises and individual entrepreneurs to make double profits in the short time and keep sustainable development. In the book, he introduces almost a hundred practical ways. Many companies just applied one of the methods and were able to earn double or several times of income in very short time.