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
Williams RE, Kalilani L, DiBenedetti DB, Zhou X, Granger AL, Fehnel SE, Levine KB, Jordan J, Clark RV. Frequency and severity of vasomotor symptoms among peri- and postmenopausal women in the United States. Climacteric. 2008 Jan 1;11(1):32-43.