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
Anderson IM, Jones S, Twiss J. Do negative cognitive style and personality predict depression symptoms and functional outcomes in severe bipolar and unipolar disorders? Int J Cogn Ther. 2009 Dec 15;2(4):343-53. doi: 10.1521/ijct.2009.2.4.343