ABSTRACT
When the manuscript is finished, I can stop the logical thinking finally. Looking at this pile of manuscript papers, I cannot help thinking of a line from a poem abstracted from Tales of Woe by Qu Yuan – ‘The road ahead will be long, yet high and low I will search with my will unbending’. When we go through the middle age, those familiar poems would always add to a new state of mind for our life. Therefore, the verse of Qu Yuan unavoidably reminds me of my previous research experiences. I like this book because it is the result of my investigation in the past years and also the forerunner of my further research in the future. Looking back on the road I have walked, I feel that it is like a gently flowing stream, the water is limpid and the source is farther and farther away. In spite of this, I will never forget that the road ahead will be long, and I will not stop my progress forward because the theories in this book are still not mature. A large amount of issues have not been touched on, and many concepts still remain to be clarified.
