Gross substitutes and endowed assignment valuations
证明了满足总替代条件的偏好类别严格大于禀赋分配估值类别，解决了Hatfield和Milgrom提出的开放问题，即并非所有可替代估值函数都能分解为单位需求估值的组合。
We show that the class of preferences satisfying the Gross Substitutes condition of Kelso and Crawford (1982) is strictly larger than the class of Endowed Assignment Valuations of Hatfield and Milgrom (2005), thus resolving the open question posed by the latter paper. In particular, our result implies that not every substitutable valuation function can be "decomposed" into a combination of unit-demand valuations.