I now turn to Freud ,from whose work the following quotation is taken.
后半句 其实应该反过来来理解 the following quotation is taken from whose work.这里的whose其实就是前句的Freud.
这种句子你就把句子按陈述语气读一下,就是说 要调换前后位置.就知道要不要加in on from这些介词了
比如：He is the person that I make friends with.这里 词组就是make friends with somebody,少了with这个介词,这个词组就不存在了,这句话就有问题了.
这是最通俗最好理解的解释了