Secondly , after a field survey of three types products aimed to 123 online and traditional retailers , a model based on the salop ( 1979 ) and hotelling ( 1929 ) , named " circular city and isolated island " model , is built to explain the empirical results 第二，对123家网上网下企业3类产品的销售价格进行了实地调查，并建立salop - hotelling “环湖孤岛”综合模型对经验研究结果进行解释。
