The paper's authors tried to take into account other factors, but they admit it may not have been entirely possible to quantify differences in, for example,the recipient's health, which can be a big factor in the success of a transplant.

VOA: standard.2010.07.14

You measure health and you measure a factor like diet, you measure other factors that might be related as well.

你衡量其健康及饮食,还有很多其他可能有关的因素

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

You measure health and you measure a factor like diet, you measure other factors that might be related as well.

你衡量其健康及饮食,还有很多其他可能有关的因素

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选