有童鞋买的是电子版的教材吗?我安装了vitalsource bookshelf,输入redeem code,也注册了,但是老是下载不了。左边已经显示CFA institue CFA curriculum 2012, 右侧是6本书,但是每个都有个感叹号,下面提示说,you don't have this book installed. Would u lilke to download it now? 我选择download,但是下载到4M左右又突然停止了。哪位童鞋能帮忙看下是咋回事吗?我截了图出来。谢谢了!