原文：
Hundreds of cases have grappled with factual situations that do not fit neatly into an offer-and-acceptance paradigm. There is also the recurring difficulty of the extent to which, if at all, an offeror should be bound by his offer.
The common law stipulates that until you accept my offer I am at liberty to withdraw it.
German,Swiss, Greek, Austrian, and Portuguese law, on the other hand, provide that I am bound by my offer; I cannot simply revoke it with impunity. A purported withdrawal has no legal effect.
为什么在German Swiss Greek…一些国家中，offer不可以随意撤回，但是在英美法系(common law)中就可以被撤回呢？具体是指哪一类的合同offer？
