Edwards PET, Parsons GR, Myers KH. The economic value of viewing migratory shorebirds on the Delaware Bay: an application of the single-site travel cost model using on-site data. Hum Dimens Wildl. 2011;16(6):435-44. doi: 10.1080/10871209.2011.608180
Maughan GL, Gnanasakthy A, Cooke DA. The effects of soil-applied granular pesticides on the establishment and yield of sugar-beet in commercial fields. Crop Prot. 1984 Dec;3(4):439-50.