An Exactly aggregable trigonometric engel curve demand system
证明了Gorman（1981）提出的收入三角函数线性需求系统确实存在，且具有较大的正则区域，解决了其存在性的疑问。
Gorman's (1981) characterization of Engel curves includes the possibility of demand systems that are, linear in trigonometric functions of income, but the actual existence of such systems has been questioned. This paper shows that such systems exist, and can have large regular regions.