Agricultural Investment and the Management of the Royal Demesne Manors, 1236–1240
研究了1236至1240年间英国皇家庄园管家沃尔特·德·伯戈通过大幅增加农业投资（达到中世纪平均水平的四到五倍），在四年内将庄园净价值提升70%，揭示了中世纪农业中投资与生产力之间的直接联系。
Between 1236 and 1240 the king's estate steward Walter de Burgo improved the productivity of about forty royal manors by systematically increasing agricultural investment to levels four to five times the medieval average. On estates where he managed the inland directly, de Burgo improved the quality of the draft animals and spent large sums on marling, smother crops, and on the purchase of foreign seed. Within four years he raised the net value of these manors 70 percent, thus demonstrating the direct link which could exist between investment levels and productivity in medieval agriculture.