Firstly, I have to buy high power laser . it is because that I need a 532nm laser pointer ( it is also should be 200mw green laser pen )for an assistant teaching aid. So I went to electronic stores named “just buy wholesale ” which wholesale various kinds of top powerful green laser. Accidently, an electronic version of /Family Album USA/ has been spotted by me and it was just near a counter which provides powerful green lasers Wow! It seems like that I finally found a teaching text book which exactly suit for my students!