· This is an update Text book for beginning graduate students in Mathematics, Probability and Statistics, Engineering, Computer Sciences, Mathematical Economics 　　 · It distinguishes from all existing texts on the subject from its pedagogical spirit, namely, motivations before mathematics; mathematics tools are only introduced when needed and motivated 　　 · All theoretical results are proved in a friendly fashion 　　 · Teaching the students, not only the concepts and possible applications, but also guiding the students with proof techniques 　　 · This series will help students to learn with full understanding and appreciation of the subject 　　 · It will provide interested students with solid background for research