9Spiro,R. J, , Faltovich,P. J. ,Jacobson ,M, J.& Coulson,R. L. ( 1992 ). Cognitive Flexibility ,Constructivism and Hipertext:Random Access Instruction for Advanced Knowledge Acquisition in Ⅲ-Structured Domains. In T. M. Duffy & D, H. Jonassen(Eds.), Constructivism and the Technology of Instruction:a Conversation (57-75 ). Hillsdale, NJ:Lawrence Erlbaum Associates.