Cain, Cortney. Chapter 4, Door County Apple Horticulture. The Development of Apple Horticulture in Wisconsin, 1850s-1950s: Case Studies of Bayfield, Crawford, and Door Counties (学位论文). 威斯康辛大學麥迪遜分校. 2006-05 [2019-09-15]. (原始内容存档于2020-11-18).
Cain, Cortney. Chapter 4, Door County Apple Horticulture. The Development of Apple Horticulture in Wisconsin, 1850s-1950s: Case Studies of Bayfield, Crawford, and Door Counties (学位论文). 威斯康辛大學麥迪遜分校. 2006-05 [2019-09-15]. (原始内容存档于2020-11-18).